var-let-const.txt

VAR-CONST-LET KEYWORDS

1.Var: Can be redeclared & Updated
Ex:
var first="hey"
var first="hello"
console.log(first);

output:hello


2.Let: Can't be redeclared but can be Updated
Ex:
let first="hey"
let first="hello"
console.log(first);

output: error

Ex:
let first="hey"
first="hello"
console.log(first);

output: hello



3.const:  can't be redeclared & updated also it must be definitely initialised with some value.
Ex:
const first="hello"
const first="hey"
console.log(first);

output: error





var have Global scope & Function scope
let,const has block scope

Ex:
for(var i=0;i<5;i++)
{
console.log(i+" ");
}
console.log("outside loop value is:"+i);

Output:
0
1
2
3
4
outside loop value is:5


Ex:
for(let i=0;i<5;i++)
{
console.log(i+" ");
}
console.log("outside loop value is:"+i);

Output:
0
1
2
3
4
outside loop value is:error//cant be accessed outside of the loop

Ex:
for(const i=0;i<5;i++)
{
console.log(i+" ");
}
console.log("outside loop value is:"+i);

Output:
0
outside loop value is:Type Error//when i changes from 0 to 1 this error appears coz its a constant it cant be changed or updated