---
# System prepended metadata

title: JAVASCRIPT

---

# JAVASCRIPT
## JAVASCRIPT OPERATOR
In javascript we have the following operators 
* Assingnment operator: This is used in the assignment of value to a variable.

E.g 
 let price = 1200
 let total = x+y
 String assignment: EG
 ````
 <!DOCTYPE html>
 <html>
     <head>
         <title>javascript</title>
    </head>
    <body>
        <h1 id="demo">
            
        </h1>
        
        <script>
             let text = "hello";
            text += "world";             
            
        document.getElementById("demo").innerHTML
           
        </script>
    </body>
</html>

This code above shows how string assignment is done.
````


 **The &&= Operator**
The Logical AND assignment operator is used between two values.
this is used to check two conditions. Both mus be true when one is false all the will print false

````
        
        <script>
             let age = 10;
            let  hasID = true;
            if (age>= 18 && hasID === true){
            console.log("you can enter")
            }
            
        </script>
````
We have other operators like "OR operator and the ?? operator".
````
<script>
let name = null;
let displayname = name ?? "guest"
console.log(displayname)
</script>

Here since name is null it it will take the one on the right hand which is guest.
````

## COMPARISM OPERATORS

Comparison operators are used to compare two values.
Comparison operators always return true or false.
Some comparism operators are the following
```
let price = 10;
let age = 10;
if(age==price){
console.log("we are equal")
}
2nd
let car = "10"
let home = "20"

//this is is not
if(car != home){
console.log("were not equal")
}

//
!== this one is : not equal or note equaletype
=== this is they mus be equaland same datatype
````
## JAVASCRIPT CONDITION.

In javascript we have the following condition statement:
*    If Statement
*    if...else
*    if...else if...else
*    switch
*    ternary (? :)


When to use Conditionals

* Use if to specify a code block to be executed, if a specified condition is true
* Use else to specify a code block to be executed, if the same condition is false
* Use else if to specify a new condition to test, if the first condition is false
* Use switch to specify many alternative code blocks to be executed
* Use (? :) (ternary) as a shorthand for if...else


**IF STATEMENT**
Use the JavaScript if statement to execute a block of code when a condition is true.


````
<p id="demo"></p>
<script></script>
if (hour < 18){
document.getElementById("demo").innerHTML = "GOOD DAY"

//NESSTED IF
Nested if statements can make your code more complex.
A better solution is to use the logical AND operator:
//USING NESSTED IF 
<script>
let age = 18
let country = nigeria
let text = "you can drive"

if(age>=18){
if (country == nigeria){
text = "you can drive"
}

}
document.getElementById("demo").innerHTML=text;

//USING LOGICAL OPERATOR
let age = 18
let country = nigeria
let textt = "you can drive "
if(age>=18 && country ==nigeria){
text= "you can drive"
}
document.getElementById("demo").innerHTML = text;

</script?>
````

The else Statement

Use the else statement to specify a block of code to be executed if a condition is false.
````

if (hour < 18) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}
````
The Else...if Statement

````
<p id="demo"></p>
<script>
const time = new Date().getHours();
let greetings;
if (time < 10) {
  greeting = "Good morning";
} else if (time < 20) {
  greeting = "Good day";
} else {
  greeting = "Good evening";
}
document.getElementById("demo").innerHTML = greeting;
</script>
````

**TENARY**
This is used in place of if...else and it is very common in modern javascript like react.

````
<script>
let price = 10
let ismember = true
let discount = ismember ? 0.2:0  //thiis means discount for members and no dicount for nonn memebers.
let total = 10 - (price * discount);
document.getElementById("demo").innerHTML = "The price is " + total;

</script>
````


## JavaScript Switch Statement
Based on a condition, switch selects one or more code blocks to be executed.
switch executes the code blocks that matches an expression.
switch is often used as a more readable alternative to many if...else if...else statements, especially when dealing with multiple possible value
````
let day;
let date = new Date().getDay();

switch (date){
case 0 
day = "Sunday";
break;
case 1
day = "Monday";
break;
case 2
day = "Tuesday";
break;
case 3 
day = "Wednesday"
break
case 4
day = "thursday"
break
case 5 
day = "Friday";
break;
case 6
day = "saturday"
break
default:
day = "looking forward to hear from you"

}
document.getElementById("demo").innerHTML = "Today is " + day;
````


