Enforce/Disallow Variable Initializations (init-declarations)

In JavaScript, variables can be assigned during declaration, or at any point afterwards using an assignment statement. For example, in the following code, foo is initialized during declaration, while bar is initialized later.

var foo = 1;
var bar;

if (foo) {
    bar = 1;
} else {
    bar = 2;
}

Rule Details

This rule is aimed at enforcing or eliminating variable initializations during declaration. For example, in the following code, foo is initialized during declaration, while bar is not.

var foo = 1;
var bar;

bar = 2;

This rule aims to bring consistency to variable initializations and declarations.

Options

This rule is configured by passing in the string "always" (the default) to enforce initialization at declaration, or "never" to disallow initialization during declaration. This rule applies to var, let, and const variables, however "never" is ignored for const variables, as unassigned consts generate a parse error.

You can configure the rule as follows:

{
    // (default) All variables must be initialized at declaration
    "init-declarations": [2, "always"],

    // Variables must not be initialized at declaration
    "init-declarations": [2, "never"]
}

When configured with "always" (the default), the following patterns are considered warnings:

function foo() {
    var bar;
    let baz;
}

The following patterns are not considered warnings with "always".

function foo() {
    var bar = 1;
    let baz = 2;
    const qux = 3;
}

When configured with "never", the following patterns are considered warnings.

function foo() {
    var bar = 1;
    let baz = 2;
}

The following patterns are not considered warnings with "never". Note that const variable initializations are ignored with "never".

function foo() {
    var bar;
    let baz;
    const buzz = 1;
}

Enforce/Disallow Variable Initializations (init-declarations)

Rule Details

Options

When Not To Use It

Version

Resources