Require let or const instead of var

Docs > Code Analysis > Static Analysis Rules > Require let or const instead of var

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Metadata

ID: javascript-code-style/no-var

Language: JavaScript

Severity: Notice

Category: Best Practices

Description

Block scoped lexical declarations like let and const are preferred over var. Block scope is common in many other programming languages and helps programmers avoid mistakes.

Non-Compliant Code Examples

var foo = bar;
var foo = bar, toast = most;
var foo = bar; let toast = most;
for (var a of b) { console.log(a); }
for (var a in b) { console.log(a); }
for (let a of b) { var c = 1; console.log(c); }
for (var i = 0; i < list.length; ++i) { foo(i) }
for (var i = 0; i < 10; ++i) {};
for (var a of b) { arr.push(() => a); }
for (let a of b) { var c; console.log(c); c = 'hello'; }
var a = a;
var {a = a} = {};
var {a = b, b} = {};
let {a, b = a} = {};
var a = b, b = 1;
let a = b; var b = 1;
function foo() { a } var a = 1; foo();
if (foo) var bar = 1;
var foo = 1;
{ var foo = 1 }
if (true) { var foo = 1 }
var foo = 1;
declare var foo = 2;
function foo() { var let; }
function foo() { var { let } = {}; }
function foo() { a }
var a = 1; foo();

Compliant Code Examples

const JOE = 'schmoe';
let moo = 'car';
const JOE = 'schmoe';
let moo = 'car';