The difference betweenvar andlet in JavaScript is block scope.

var

When avar is declared outside a block scope, and then re declared inside a block after the first declaration. The value of thevar gets changed after the block scope is over.

//first declaration of var xvarx=10;{//second declaration of var xvarx=5;alert(x);//prints 5}alert(x);//prints 5

let

However by usinglet keyword to declare a variable. the value of the variable doesn't get changed by the subsequent re declaration inside the block.

//first declaration of let var ylety=15;{//second declaration of let var ylety=90;alert(y);//prints 90}alert(y);//prints 15