---
# System prepended metadata

title: JavaScript Challenge
tags: [Codetisan - JavaScript]

---

---
tags: Codetisan - JavaScript
title: JavaScript Challenge
description: Coding Problems
---
## Sort letters in alphabetical order
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw1oigoc01800vl642aww161/javascript/sort-letters-in-alphabetical-order)

Sort the letters of a given string in alpabetical order.

Sample Code:

```javascript
function sortLetter(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'codetisan'
Output: 'acdeinost'
Explanation: The letters of the output are sorted in alphabetical order.
```

```code
Input: 'letter'
Output: 'eelrtt'
Explanation: The letters of the output are sorted in alphabetical order.
```

Submission:

```javascript
const sortLetter = (str) => str.split('').sort((a, b) => a.localeCompare(b)).join('');
```

## Convert positive integers to negative integers
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1ngbg1e17540wmm9skkrdkk/javascript/constant-negative)

Given a number, return the number with a negative sign.

Sample Code:

```javascript
function negNum(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 5
Output: -5
Explanation: The input number has been converted to a negative number.
```

```code
Input: -1
Output: -1
Explanation: The input is already a negative number.
```

Submission:

```javascript
const negNum = (num) => num > 0 ? -num : num;
```

## Remove first and last letters
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1ngvc5o01030ul79jrq0pb4/javascript/removing-letters)

Given a string, return the string without its first and last characters.

Sample Code:

```javascript
function lettersRmv(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: 'odetisa'
Explanation: The first and last letters have been removed.
```

```code
Input: '01'
Output: ''
Explanation: The first and last letters have been removed.
```

Submission:

```javascript
const lettersRmv = (str) => str.slice(1, -1);
```

## Starting elements in String
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1p6eyjv01890vl4y8afsahw/javascript/starting-elements)

Return true if the given string starts with 'Code'.

Sample Code:

```javascript
function startsWith(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: true
Explanation: 'Codetisan' starts with 'Code'.
```

```code
Input: 'meow'
Output: false
Explanation: 'meow' does not start with 'Code'.
```

Submission:

```javascript
const startsWith = (str) => str.startsWith('Code');
```

## Extract the first element of an Array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1osz47n00980vmjc3ytk0wj/javascript/the-first-element)

Given an array, return the very first element.

Sample Code:

```javascript
function firstEle(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,4]
Output: 1
Explanation: Element 1 has an index value of zero.
```

```code
Input: [[1,2],[3,4]]
Output: [1,2]
Explanation: Element [1,2] has an index value of zero.
```

Submission:

```javascript
const firstEle = (arr) => arr[0];
```

## Get the largest even number from an array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw26pfan03950wjxufbb7517/javascript/get-the-largest-even-number-from-an-array)

Given an integer array, get the largest even number from the array, return -1 if not found.

Sample Code:

```javascript
function getTheLargest(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [2,3,4,10,5,8]
Output: 10
Explanation: The largest even number in the array is 10.
```

```code
Input: [3,1,9,17]
Output: -1
Explanation: Cannot find the largest even number, return -1 instead.
```

Submission:

```javascript
const getTheLargest = (arr) => {
    arr.sort((a, b) => b - a);
    for (let i of arr) {
        if (i % 2 === 0) {
            return i;
        }
    }
    return -1;
};
```

## Keywords detector
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1n9ew5b05920vlc58cavhk1/javascript/keywords-detector)

Return true if the input contains "girlfriend". Otherwise false.


Sample Code:

```javascript
function spotCheck(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'I have a girlfriend on my monitor.'
Output: true
Explanation: "girlfriend" to be found in the input.
```

```code
Input: 'This world shall know code.'
Output: false
Explanation: "girlfriend" 404 not found!
```

Submission:

```javascript
const spotCheck = (str) => str.includes('girlfriend');
```

## Retirement age
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1qlixgt00920wjy5lck3sj5/javascript/retirement-age)

Given your today’s years old, how many more years until retirement?
Assuming 60 years old is the age for retiring.

Sample Code:

```javascript
function retireYears(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 60
Output: 'You are ready to retire.'
Explanation: 60 - 60 = 0
```

```code
Input: 1
Output: 'You have 59 more years to go.'
Explanation: 60 - 1 = 59
```

Submission:

```javascript
const retireYears = (num) => num < 60 ? `You have ${60 - num} more years to go.` : 'You are ready to retire.';
```

## Simple addition
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1otf94302430vmjqe20apo6/javascript/number-plus-one)

Given a number, increase the number by 1 and return a new value.

Sample Code:

```javascript
function plusOne(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 1
Output: 2
Explanation: 1 + 1 = 2
```

```code
Input: -999
Output: -998
Explanation: -999 + 1 = -998
```

Submission:

```javascript
const plusOne = (num) => num + 1;
```

## Masking credit card number
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1nbqkns02950vm80st16yze/javascript/convert-letters-into-asterisk-symbol)

Given a number and an integer (n), return a new string as shown in the examples.

Sample Code:

```javascript
function coverUp(num,n) {
// Enter your logic here...
}
```

Examples:

```code
Input: 123456,3
Output: '***456'
Explanation: The first 3 numbers have been replaced by asterisk symbols.
```

```code
Input: 12345678,4
Output: '****5678'
Explanation: The first 4 numbers have been replaced by asterisk symbols.
```

Submission:

```javascript
const coverUp = (num, n) => {
    for (let i = 0; i < n; i ++) {
        num = num.toString().replace(/[0-9]/, '*');
    }
    return num;
}
```

## Inspect ASCII value
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1p79ex405510wl559jrf341/javascript/ascii-value)

Return the ASCII value of the given input.

Sample Code:

```javascript
function asciiVal(inp) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'a'
Output: 97
Explanation: The character code for 'a' is 97.
```

```code
Input: 0
Output: 48
Explanation: The character code for 0 is 48.
```

Submission:

```javascript
const asciiVal = (inp) => inp.charCodeAt();
```

## Every numbers must be less than 100
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1p08w5o00050wml0fua5auw/javascript/every-numbers-are-less-than-100)

GIven an array, return true if every element are < 100.
Otherwise false. 


Sample Code:

```javascript
function hundredLess(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [-1,0,1,2,99.9]
Output: true
Explanation: Every number in the array are less than 100.
```

```code
Input: [-1,0,1,2,999.9]
Output: false
Explanation: At least one of the elements is not less than 100.
```

Submission:

```javascript
const hundredLess = (arr) => arr.every(i => i < 100);
```

## Determine the length of a String
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q78e3n24430wjx1qdi2tfn/javascript/counting-stars)

Return the amount of character in the given string.

Sample Code:

```js
function letterCount(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: 9
Explanation: There are 9 characters to be found.
```

```code
Input: ' Java Javascript '
Output: 17
Explanation: 17 characters to be found. Yes, including the spaces.
```

Submission:

```javascript
const letterCount = (str) => str.length;
```

## Largest number in the Array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1qqfaeh00160wlgy9o4udy3/javascript/largest-number-in-the-array)

GIven an array of numbers, return the largest number.

Sample Code:

```javascript
function topNum(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,3,4,5,3,9]
Output: 9
Explanation: 9 is the largest value among all the elements.
```

```code
Input: [-1,-2,0,-3,-4]
Output: 0
Explanation: 0 is the largest value among all the elements.
```

Submission:

```javascript
const topNum = (arr) => Math.max(...arr);
```

## Add Two Numbers
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckvg8oykk00800wml87uzlaa3/javascript/add-two-numbers)

Given the first input n1 and second input n2, calculate the sum of n1 + n2 and return the sum.

Sample Code:

```javascript
function sum(n1, n2) {
// Enter your logic here...
}
```

Examples:

```code
Input: n1=1, n2=1
Output: 2
Explanation: The sum of 1 and 1 equals to 2
```

```code
Input: n1=2, n2=-2
Output: 0
Explanation: The sum of 2 and -2 equals to 0
```

Submission:

```javascript
const sum = (n1, n2) => n1 + n2;
```

## Calculate the sum of positive numbers in an Array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1nj3zum00330wlc3vmah67i/javascript/sum-of-positive-numbers)

Given an array of numbers, return the summation of all positive numbers in the array.

Sample Code:

```js
function sumPos(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,-999]
Output: 6
Explanation: The positive numbers are 1,2,3.
```

```code
Input: [1,-2,-3,-999]
Output: 1
Explanation: The only positive number is 1.
```

Submission:

```javascript
const sumPos = (arr) => arr.reduce((temp, i) => i > 0 ? temp + i : temp, 0);
```

## Extract the first four String elements
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1otx6ng01450xmidx70flhj/javascript/first-four-letters)

Return the first 4 letters of the given string.

Sample Code:

```js
function firstFour(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: 'Code'
Explanation: Elements from index 0 to 3 will be returned.
```

```code
Input: '01100011'
Output: '0110'
Explanation: Elements from index 0 to 3 will be returned.
```

Submission:

```javascript
const firstFour = (str) => str.slice(0, 4);
```

## Joining two Arrays without duplicate elements
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q1vuor02940wl9m5b6j3uc/javascript/joining-two-arrays-without-duplicate-elements)

Given two arrays, arr1 and arr2. 
Return a new array containing all the elements from both arr1 and arr2 without any duplicates.

Sample Code:

```javascript
function joinArr(arr1,arr2) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3],[1,2,3]
Output: [1,2,3]
Explanation: The removed duplicates are 1,2, and 3.
```

```code
Input: ['Javascript','ReactJS','NodeJS'], ['Typescript','ReactJS','NextJS']
Output: ['Javascript','ReactJS','NodeJS','Typescript','NextJS']
Explanation: The removed duplicate is 'ReactJS'.
```

Submission:

```javascript
const joinArr = (arr1, arr2) => Array.from(new Set(arr1.concat(arr2)));
```

## Check whether digits of an integer has an increasing sequence
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw26pz4z00760wlbjrr1vtsz/javascript/check-whether-digits-of-an-integer-has-an-increasing-sequence)

Given an integer, check whether digits of the integer has an increasing sequence.

Sample Code:

```javascript
function isIncreasing(number) {
// Enter your logic here...
}
```

Examples:

```code
Input: 1234
Output: true
Explanation: 1,2,3,4 is an increasing sequence.
```

```code
Input: 2571
Output: false
Explanation: 2,5,7,1 is not an increasing sequence.
```

Submission:

```javascript
const isIncreasing = (number) => {
    const arr = number.toString().split('');
    for (let i = 0; i < arr.length - 1; i ++) {
        if (parseInt(arr[i]) >= parseInt(arr[i + 1])) {
            return false;
        }
    }
    return true;
}
```

## Determine the length of an array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw4vbj6a015812l51p0vrmw9/javascript/determine-the-length-of-an-array)

Calculate and return the length of an array.

Sample Code:

```javascript
function calcSize(a) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,4,5]
Output: 5
Explanation: There are 5 elements in the given array.
```

```code
Input:  []
Output: 0
Explanation: Given array is empty.
```

Submission:

```javascript
const calcSize = (a) => a.length;
```

## Comparing Arrays
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q48mam03750vl332wkratl/javascript/comparing-arrays)

Perform a simple comparison between the given arrays. Return true if both the arrays carry the same elements and elements order. Otherwise false.

Sample Code:

```javascript
function compArr(arr1,arr2) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3, {key:value}],[1,2,3,{key:value}]
Output: true
Explanation: Both have the same elements and elements order.
```

```code
Input: [1,2,3],[1,2,'3']
Output: false
Explanation: '3' is not equivalent to 3 due to different data types.
```

Submission:

```javascript
const compArr = (arr1, arr2) => JSON.stringify(arr1) === JSON.stringify(arr2);
```

## Finding out data type
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1qo3mj500360wjlgm1iyj7e/javascript/finding-out-data-type)

Return the data type of the given input.

Sample Code:

```javascript
function naniTheWhat(inp) {
// Enter your logic here...
}
```

Examples:

```code
Input: true
Output: 'boolean'
Explanation: Boolean type has two values. True and false.
```

```code
Input: ' '
Output: 'string'
Explanation: Anything inside the quotation is considered as string. 
```

Submission:

```javascript
const naniTheWhat = (inp) => typeof(inp);
```

## Some are even numbers
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1p3tp6i09590wl7be3pw4pc/javascript/some-are-even-numbers)

Return true if the given array consists of even numbers.
Otherwise false.

Sample Code:

```javascript
function someEven(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,4,5]
Output: true
Explanation: 2 and 4 are even numbers.
```

```code
Input: [1,'Happy',3,'Coding',5]
Output: false
Explanation: There are no even numbers.
```

Submission:

```javascript
const someEven = (arr) => arr.some(i => i % 2 === 0);
```

## Count the number of vowels in a given string
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw1rc7f2013211mlfxnqk2nj/javascript/count-the-number-of-vowels-in-a-given-string)

Count the number of vowels appeared in a given string.

Sample Code:

```javascript
function countVowel(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: 4
Explanation: 'Codetisan' contains 4 vowels (o, e, i, a)
```

```code
Input: 'shhhh'
Output: 0
Explanation: 'shhhh' has no vowel.
```

Submission:

```javascript
const countVowel = (str) => str.match(/[aeiou]/gi) === null ? 0 : str.match(/[aeiou]/gi).length;
```

## Say no to hardcoding
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1nd6s4207290wmmb7vx6a1p/javascript/say-no-to-hardcoding)

Create a function that receives a number and return the output as shown in the examples.
Here is your arrow: →

Sample Code:

```javascript
function noHardcode(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 3
Output: 'There are 3 arrows→→→'
Explanation: There are 3 arrows.
```

```code
Input: 0
Output: 'There are 0 arrow'
Explanation: There are 0 arrow.
```

Submission:

```javascript
const noHardcode = (num) => {
    let arrow = '';
    for (let i = 0; i < num; i ++) {
        arrow += '→';
    }
    return `There are ${num} ${num !== 0 ? `arrows${arrow}` : 'arrow'}`
}
```

## Truthy and falsy values
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q7qtqa02150vkx9ff87duj/javascript/truthy-and-falsy-values)

Based on the input, return a boolean value.

Sample Code:

```javascript
function trueFalse(inp) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Javascript'
Output: true
Explanation: String is a truthy value.
```

```code
Input: ''
Output: false
Explanation: Empty string is a falsy value.
```

Submission:

```javascript
const trueFalse = (inp) => inp !== '';
```

## Removing whitespace
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1ufos6k01870vmdaqc6jcx3/javascript/removing-whitespace)

Given a string, remove leading or trailing whitespaces and return a new string.

Sample Code:

```javascript
function rmvSpace(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Tom and Jerry '
Output: 'Tom and Jerry'
Explanation: Whitespaces are removed from both sides of the string.
```

```code
Input: '  Javascript  '
Output: 'Javascript'
Explanation: Whitespaces are removed from both sides of the string.
```

Submission:

```javascript
const rmvSpace = (str) => str.trim();
```

## Convert a number to hours and minutes
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw1k7s6g000012joqnpfxngr/javascript/convert-a-number-to-hours-and-minutes)

Write a JavaScript function to convert a given number in minutes to hours and minutes.

Sample Code:

```javascript
function convertTime(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 235
Output: '3:55'
Explanation: 235 is equal to 3 hours and 55 minutes.
```

```code
Input: 1060
Output: '17:40'
Explanation: 1060 is equal to 17 hours and 40 minutes.
```

Submission:

```javascript
const convertTime = (num) => `${~~(num / 60)}:${num % 60}`
```

## Array creation
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1qc2ihb00850wl8074um8xj/javascript/array-creation)

Given two inputs, return an array containing those two inputs.

Sample Code:

```javascript
function createArray(inp1,inp2) {
// Enter your logic here...
}
```

Examples:

```code
Input: {obj: 1}, [2]
Output: [{obj: 1}, [2]]
Explanation: The two inputs have now been stored in an array as elements.
```

```code
Input: ' ',0
Output: [' ',0]
Explanation: The two inputs have now been stored in an array as elements.
```

Submission:

```javascript
const createArray = (inp1, inp2) => [...[inp1], ...[inp2]];
```

## Spaceless String
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1np470s19180vmnmq5e4bri/javascript/spaceless)

Given a string, return the string without any spaces.

Sample Code:

```javascript
function noSpace(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: ' Codetisan '
Output: 'Codetisan'
Explanation: There are no spaces available anywhere in the output string.
```

```code
Input: 'Binary
code: 0 1'
Output: 'Binarycode:01'
Explanation: Binary is followed by a newline, so the newline must also be removed.
```

Submission:

```javascript
const noSpace = (str) => str.replace(/ |\n/ig, '');
```

## Append a new element to a given array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw5wy4tv00740wmd40zbp4jf/javascript/append-a-new-element-to-a-given-array)

Write a JavaScript function to accept 2 parameters, an array and a new value. Append the new value to the given array and return the updated array.

Sample Code:

```javascript
function append(arr, value) {
// Enter your logic here...
}
```

Examples:

```code
Input: ['hello','world'], 'hi'
Output: ['hello','world','hi']
Explanation: Add the new value to the end of an given array. 
```

```code
Input:  [1,2,3], 4
Output: [1,2,3,4]
Explanation: Add the new value to the end of an given array. 
```

Submission:

```javascript
const append = (arr, value) => [...arr, ...[value]];
```

## Capitalize the first character
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw0qu68o00460wl0219xeetk/javascript/capitalize-the-first-character)

Capitalize the first character of each word of a given string.

Sample Code:

```javascript
function capitalize(s) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'hello world'
Output: 'Hello World'
Explanation: Capitalize letter h and w.
```

```code
Input: '3 cars'
Output: '3 Cars'
Explanation: Capitalize letter c.
```

Submission:

```javascript
const capitalize = (s) => s.split(' ').map((e) => e.substr(0, 1).toUpperCase() + e.substr(1)).join(' ');
```

## Find the sum of elements in a given integer array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckw4rczz704250wl3nijw5jm4/javascript/find-the-sum-of-elements-in-a-given-integer-array)

Find the sum of elements in a given integer array.

Sample Code:

```javascript
function sum(s) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,4,5]
Output: 15
Explanation: 1 + 2 + 3 + 4 + 5 = 15
```

```code
Input:  [-10, 10, 1, -1, 100]
Output: 100
Explanation: -10 + 10 + 1 - 1 + 100 = 100
```

Submission:

```javascript
const sum = (s) => s.reduce((a, b) => a + b);
```

## Flattening sub-arrays in an Array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1u3p20h00250wmmrt280j4x/javascript/reducing-sub-arrays)

Given an array with multiple subarray elements, the final function needs to flatten the array to ensure that the array does not contain subarrays.

Sample Code:

```javascript
function flatArr(arr) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,[4,5],['numbers']]
Output: [1,2,3,4,5,'numbers']
Explanation: The sub-array elements have been flattened.
```

```code
Input: [1,[2,[3],4],5]
Output: [1,2,3,4,5]
Explanation: The sub-array elements have been flattened.
```

Submission:

```javascript
const flatArr = (arr) => arr.flat(Infinity);
```

## Adding element to the beginning of an Array
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1tbqbtu02440wijy6urxnaz/javascript/adding-element-to-the-beginning-of-an-array)

Given an array and a value, insert the value to the beginning of the array.

Sample Code:

```javascript
function addEle(arr,ele) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3],0.9
Output: [0.9,1,2,3]
Explanation: Element 0.9 has been added to the array at index 0.
```

```code
Input: [1,2,3],[0,'0.5']
Output: [[0,'0.5'],1,2,3]
Explanation: Element [0,'0.5'] has been added to the array at index 0.
```

Submission:

```javascript
const addEle = (arr, ele) => {
    arr.unshift(ele);
    return arr;
}
```

## Number to string
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q93u0q18120wl4k5joscoq/javascript/number-to-string)

Return the given number in a string format.

Sample Code:

```javascript
function numToStr(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 0
Output: '0'
Explanation: Number in string format.
```

```code
Input: -99.99
Output: '-99.99'
Explanation: Number in string format.
```

Submission:

```javascript
const numToStr = (num) => '' + num;
```

## Round down
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1rs1yls03830wl0w1a88a9n/javascript/round-down)

Round down the given number.

Sample Code:

```javascript
function roundDown(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 9.9
Output: 9
Explanation: 9 is the result of rounding down 9.9.
```

```code
Input: 0.1
Output: 0
Explanation: 0 is the result of rounding down 0.1.
```

Submission:

```javascript
const roundDown = (num) => Math.floor(num);
```

## Duplicate elements
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1p4qfy200250wkw6u88w76l/javascript/double-elements)

Return the given string with 2 occurrences for each elements.

Sample Code:

```javascript
function doubleUp(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Hello World'
Output: 'HHeellllloo WWoorrlldd'
Explanation: Every Elements have its own duplication.
```

```code
Input:  'ಠ_ಠ'
Output: 'ಠಠ__ಠಠ'
Explanation: Symbols are also being duplicated.
```

Submission:

```javascript
const doubleUp = (str) => str.split('').map((e) => e + e).join('');
```

## Speed of light
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1ow5f0i01060vjpe4jeiofu/javascript/speed-of-light)

Return true if the given number is equivalent to 299,792,458.
Otherwise false.


Sample Code:

```javascript
function lightSpeed(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 299792458
Output: true
Explanation: 299,792,458 m/s is the speed of light, according to Google.
```

```code
Input: 323232
Output: false
Explanation: 299,792,458 m/s is the speed of light, according to Google.
```

Submission:

```javascript
const lightSpeed = (num) => num === 299792458;
```

## Extract the first string element
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1q67cvk10080wl889dviekn/javascript/first-letter)

Return the first letter of the given string.

Sample Code:

```javascript
function firstLetter(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'Codetisan'
Output: 'C'
Explanation: 'C' element has an index value of 0.
```

```code
Input: ' Javascript'
Output: ' '
Explanation: ' ' element has an index value of 0.
```

Submission:

```javascript
const firstLetter = (str) => str.split('')[0]; 
```

## 100 plus
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1m9km7e03970wmmabksxyh3/javascript/100-plus)

A function that receives two numbers, return true if the summation of the numbers is less than or equal to 100.

Sample Code:

```javascript
function hundredPlus(num1,num2) {
// Enter your logic here...
}
```

Examples:

```code
Input: 1,100
Output: false
Explanation: 1+100 equals to 101 which is not less than 100 or equal to 100.
```

```code
Input: 50,50
Output: true
Explanation: 50+50 is equal to 100.
```

Submission:

```javascript
const hundredPlus = (num1, num2) => num1 + num2 === 100;
```

## Printing the next character
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1nqp4bq00370vkzzdpq31hj/javascript/printing-the-next-character)

Given a string, replace every letter with its subsequent letter. For example, the letter A will be converted to letter B.

Sample Code:

```javascript
function nextTerm(str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'abcd'
Output: 'bcde'
Explanation: The subsequent letter 'a' is 'b'.
```

```code
Input: 'bncd'
Output: 'code'
Explanation: The subsequent letter 'b' is 'c'.
```

Submission:

```javascript
const nextTerm = (str) => str.split('').map((e) => String.fromCharCode(e.charCodeAt() + 1)).join('');
```

## Find the largest of three given integers
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/ckvxx42mb000012mgbqbxmorg/javascript/find-the-largest-of-three-given-integers)

Write a JavaScript function to accept 3 integers, find the largest of three given integers.

Sample Code:

```javascript
function findTheLargest(a, b, c) {
// Enter your logic here...
}
```

Examples:

```code
Input: 1,2,3
Output: 3
Explanation: Integer 3 is the largest of three given integers.
```

```code
Input: 100,-200,50
Output: 100
Explanation: Integer 100 is the largest of three given integers.
```

Submission:

```javascript
const findTheLargest = (a, b, c) => Math.max(a, b, c);
```

## -Counting steps
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1qml7ai01210wievos5bezf/javascript/counting-steps)

Return an array of numbers starting with 1 up to the given number. Round up the number if the given number has decimal places.

Sample Code:

```javascript
function myLegHurts(num) {
// Enter your logic here...
}
```

Examples:

```code
Input: 10
Output: [1,2,3,4,5,6,7,8,9,10]
Explanation: Each numbers have been increased by 1 up to number 10.
```

```code
Input: 5.5
Output: [1,2,3,4,5,6]
Explanation: Each numbers have been increased by 1 up to number 6.
```

Submission:

```javascript
const myLegHurts = (num) => {
    const arr = [];
    for (let i = 1; i <= Math.ceil(num); i ++) {
       arr.push(i);
    }
    return arr;
}
```

## Introduce yourself
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1xmtfsg03250wl8ss9l900q/javascript/introduce-yourself)

Build and return a sentence using the given Object as shown in the example.

Sample Code:

```javascript
function whatAmI(obj) {
// Enter your logic here...
}
```

Examples:

```code
Input: {name:‘human’,lang:’English‘}
Output: ’I am human and I speak English.‘
Explanation: ‘human’ and ‘English’ are the first and second values of the object respectively.
```

```code
Input: {name:‘another human’,lang:‘Javascript’}
Output: ‘I am another human and I speak Javascript.’
Explanation: ‘another human’ and ‘Javascript’ are the first and second values of the object respectively.
```

Submission:

```javascript
const whatAmI = (obj) => `I am ${obj.name} and I speak ${obj.lang}.`
```

## Keywords detector II
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1vvv12n02160wl11wd2tm4a/javascript/keywords-detector-ii)

Given a string and a keyword, return the keyword index value as shown in the examples.

Sample Code:

```javascript
function wordFinder(strs,str) {
// Enter your logic here...
}
```

Examples:

```code
Input: 'What did the ocean say to the beach','beach'
Output: 'beach found at index 7.'
Explanation: The element 'beach' has an index value of 7.
```

```code
Input: 'Nothing, it just waved','🐳'
Output: '🐳 not found.'
Explanation: The element '🐳' was not found in the input string.

```

Submission:

```javascript
const wordFinder = (strs, str) => strs.indexOf(str) === -1 ? `${str} not found.` : `beach found at index ${strs.split(' ').indexOf(str)}.`;
```

## Creating subarrays
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1ugnn2500330xml55rkeh3t/javascript/creating-nested-arrays)

The function will divide the original array into a number of sub-arrays according to the provided number N, each sub-array should have N elements.

Sample Code:

```javascript
function arrNested(arr,n) {
// Enter your logic here...
}
```

Examples:

```code
Input: [1,2,3,4,5,6],2
Output: [[1,2],[3,4],[5,6]]
Explanation: Each sub-arrays have 2 elements.
```

```code
Input: [1,2,3,4,5,6],3
Output: [[1,2,3],[4,5,6]]
Explanation: Each sub-arrays have 3 elements.
```

Submission:

```javascript
const arrNested = (arr, n) => {
    let res = [];
    while (arr.length) {
        res.push(arr.splice(0, n));
    }
    return res;
}
```

## Is remainder equals to 0
Challenge here：[Coding problems | Codetisan](https://www.codetisan.com/en/code/cl1uatlq600800vl8qvhq35nc/javascript/getting-a-0-remainder)

The given parameters are n1 and n2, the function needs to judge whether there is a remainder after n1 is divided by n2.

Sample Code:

```javascript
function isDivisible(n1,n2) {
// Enter your logic here...
}
```

Examples:

```code
Input: 1,2
Output: false
Explanation: 1 divided by 2 has a remainder, returns false.
```

```code
Input: 2,1
Output: true
Explanation: 2 divided by 1 has a remainder of 0 and returns true.
```

Submission:

```javascript
const isDivisible = (n1, n2) => n1 % n2 === 0;
```