---
# System prepended metadata

title: 作業2 JavaScript 基礎練習

---

# 作業2 JavaScript 基礎練習 
### D0971395 池間祐貴
# 1.from Python to JavaScript 
## 變數宣告（Declarations）
javaScript有三種宣告方式

var：宣告一個可隨意更改其內容的變數

let：宣告一個可隨意更改其內容的區塊區域變數

const：宣告一個只可讀取的不可變常數

javaScript:
![](https://i.imgur.com/U8S6OPj.png)

Python:
![](https://i.imgur.com/JjgQP9v.png)

基本上在javaScript code的最後面要寫「；」。

## 輸出 
javaScript的輸出方式是「console.log()」

javaScript:
![](https://i.imgur.com/dXuinBm.png)

Python:
![](https://i.imgur.com/yhoxy8E.png)

## 流程控制 - 判斷式 
javaScript用 if，else if 和 else。

javaScript:
![](https://i.imgur.com/ZRhARX3.png)

Python:
![](https://i.imgur.com/jszsmBp.png)


## 流程控制 - 迴圈 while,for
while寫法的話，大部分一樣。
但是for寫法的話，有差異。

javaScript:
![](https://i.imgur.com/NuKnW5m.png)

Python:
![](https://i.imgur.com/6A0ADZc.png)

javaScript與python可以用 continue 和 break。


## 流程控制 - switch
Python沒有switch

javaScript:
![](https://i.imgur.com/CnM8tmI.png)


# 2. Quiz 30 題

### (1) Create a variable called carName, assign the value Volvo to it.
```
var carName = Volvo;
```


### (2) Create a variable called x, assign the value 50 to it.
```
var x = 50;
```


### (3) Display the sum of 5 + 10, using two variables: x and y.
```
var x = 5;
var y = 10;
document.getElementById("demo").innerHTML = x + y;
```

### (4) Create a variable called z, assign x + y to it, and display the result in an alert box.
```
var x = 5;
var y = 10;
var z = x + y;
alert(z);
```


### (5) On one single line, declare three variables with the following names and values:
### firstName = "John" , lastName = "Doe" , age = 35
```
var firstName = "John", lastName = "Doe" , age = 35;
```


### (6) Multiply 10 with 5, and alert the result:
```
alert = (10 * 5);
```


### (7) Divide 10 by 2, and alert the result:
```
alert = (10 / 2);
```



### (8) Alert the remainder when 15 is divided by 9.
```
alert = (15 % 9);
```
### (9) Use the correct assignment operator that will result in x being 15 (same as x = x + y).
```
x = 10;
y = 5;
x += y;
```
### (10) Use the correct assignment operator that will result in x being 50 (same as x = x * y).
```
x = 10;
y = 5;
x *= y;
```
### (11) Use comments to describe the correct data type of the following variables:
```
let length = 16;          // Number
let lastName = "Johnson"; // String
const x = {
  firstName: "John",
  lastName: "Doe"
};                        // Object
```
### (12) Execute the function named myFunction.
```
function myFunction() {
  alert("Hello World!");
}
myFunction();
```
### (13) Create a function called "myFunction".
```
function myFunction(){
    alert("Hello World!");
}
```
### (14) Make the function return "Hello".
```
function myFunction() {
   return "Hello";
}
document.getElementById("demo").innerHTML = myFunction();
```
### (15) Make the function display "Hello" in the inner HTML of an element with the ID "demo".
```
function myFunction() {
  document.getElementById("demo").innerHTML = "Hello";
}
```
### (16) Alert "John" by extracting information from the person object.
```
const person = {
  firstName: "John",
  lastName: "Doe"
};

alert(person.firstName);
```
### (17) Add the following property and value to the person object: country: Norway.
```
const person = {
  firstName: "John",
  lastName: "Doe",
  country: "Noeway": 
};
```
### (18) Create an object called person with name = John, age = 50. Then, access the object to alert("John is 50").
```
const person = {
  name: "John", age: 50
};
alert(person.name + " is " + person.age);
```
### (19) The <button> element should do something when someone clicks on it. Try to fix it!
```
<button onclick = "alert('Hello')">Click me.</button>
```

### (20) When the button is clicked, the function "myFunction" should be executed.
```
<button onclickn = "myFunction">Click me.</button>
```
### (21) he <div> element should turn red when someone moves the mouse over it.
```
<div onmouseover = "this.style.backgroundColor='red'">myDIV.</div>
```
### (22) Use the length property to alert the length of txt.
```
let txt = "Hello World!";
let x = txt.length;
alert(x);
```
### (23) Use escape characters to alert We are "Vikings".
```
let txt = "We are \"Vikings\"";
alert(txt);
```
### (24) Concatenate the two strings to alert "Hello World!".
```
let str1 = "Hello ";
let str2 = "World!";
alert(str1 + str2);
```
### (25) Convert the text into an UPPERCASE text:
```
let txt = "Hello World!";
txt = txt.toUpperCase();
```
### (26) Use the slice method to return the word "bananas".
```
let txt = "I can eat bananas all day";
let x = txt.slice(10,17);
```
### (27) Use the correct String method to replace the word "Hello" with the word "Welcome".
```
let txt = "Hello World";
txt = txt.replace("Hello", "Welcome");
```
### (28) Convert the value of txt to upper case.
```
let txt = "Hello World";
txt = txt.toUpperCase();
```
### (29) Convert the value of txt to lower case.
```
let txt = "Hello World";
txt = txt.toLowerCase();
```
### (30) Get the value "Volvo" from the cars array.
```
const cars = ["Saab", "Volvo", "BMW"];
let x = cars[1];
```


