What are the Differences Between var, let, and const?

When no keyword is used, the variable will be assigned to the global object which is the window if we are in a browser. There are three keywords in JavaScript you can use for variable declarations. These are:

var
This is the default: it creates a function scoped variable which can be reassigned or redeclared later on.

let
This was introduced in ES6 and it is the preferred way over using var. It creates a block-scoped variable which can be reassigned but can’t be redeclared.

const
It was introduced in ES6 along with let. It also creates a block-scoped variable but this can’t be reassigned nor redeclared. const should be used when you don’t want to reassign a value later on.

It’s also good to mention that all declarations will be hoisted to the top of their scope.

var should be avoided if can, use let or const instead.

50 JavaScript Interview QuestionsAnd their answers explainedHere are 50 JavaScript interview questions that often come up during a technical interview. In one place, one resource to learn from.Learn More

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Resources:

• The var keyword
• The let keyword
• The const keyword