Let vs var

2 snippets in JavaScript

Also written as var vs let

JSJavaScript

syntax

let variableName = value;

example

let score = 0;
score = 10;
console.log(score);

output

Note Block-scoped. Cannot be re-declared in the same scope. Preferred for values that change.

syntax

var variableName = value;

example

function demo() {
  if (true) {
    var leaked = "visible outside block";
  }
  console.log(leaked);
}
demo();

output

"visible outside block"

Note Function-scoped, not block-scoped. Hoisted to the top of the function. Avoid in modern code -- use let or const instead.