when to use var in javascript code example

Example 1: js variables

//Making variables with let:
let numberOfFriends = 1;

//Incrementing:
numberOfFriends += 3; //numberOfFriends is now 4

// Variables with const
const minimumAge = 21; //CANNOT REASSIGN!

//Booleans - true or false values
true;
false;
let isHappy = true;

//Naming Conventions
// Use upper camel-cased names:
let numberOfChickens = 6; //GOOD
// NOT THE JS WAY:
// let number_of_chickens = 6;

Example 2: js var

var a;
console.log(a);                // scrive in console "undefined" o "" a seconda del browser usato.
console.log('still going...'); // scrive in console "still going...".

Example 3: variables in js

Variables can have anything, you define them as equal to something
    
    eg:   var x = 22
    var statement = 'hello!'
    var isAbool = true 
    
    there are three types of variables:
1. var 
2. let
3. const 

var is a normal variable
let is a variable whose value can be changed eg: let h = 12, h = 10(we changed the value, if you run this, there will be no error)
const is a variable whose value cannot be changed, if you change the value of a const, you will have errors in you code

Example 4: how to define variable in javascript

var <variable-name>;

var <variable-name> = <value>;

Example 5: variables javascript

var example = "hello";
document.write(example);// it will say hello when it runs

Example 6: js var

var a = 0, b = 0;