var vs let vs const javascript code example
Example 1: let vs const
`const` is a signal that the identifier won't be reassigned.
`let` is a signal that the variable may be reassigned, such as a counter in a
loop, or a value swap in an algorithm.
It also signals that the variable will be used only in the block it's defined
in, which is not always the entire containing function.
Example 2: what is the difference between let and const in javascript
The difference is that with const you can only only assign a value to a variable
once, but with let it allows you to reassign after it has been assigned.
Example 3: difference between var let and const in javascript with example
//functional scope
var a; // declaration
a=10; // initialization;
//global scope
// re-initialization possible
let a;//only blocked scope & re-initialization possible
a=10;
let a =20;
if(true){
let b =30;
}
console.log(b); // b is not defined
const // const also blocked scope,Re-initialization and re-declaration not possible
const a; // throws error {when we declaring the value we should assign the value.
const a =20;
if(true){
const b =30;
}
console.log(b); // b is not defined
console.log(a); // no output here because code execution break at leve b.
Example 4: var vs let vs const typescript
let num1:number = 1;
function letDeclaration() {
let num2:number = 2;
if (num2 > num1) {
let num3: number = 3;
num3++;
}
while(num1 < num2) {
let num4: number = 4;
num1++;
}
console.log(num1); //OK
console.log(num2); //OK
console.log(num3); //Compiler Error: Cannot find name 'num3'
console.log(num4); //Compiler Error: Cannot find name 'num4'
}
letDeclaration();