no-eq-null

Disallow null comparisons without type-checking operators

Comparing to null without a type-checking operator (== or !=) can have unintended results as the comparison will evaluate to true when comparing not just to null, but also to undefined.

if (foo == null) {
  bar();
}
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Rule Details

The no-eq-null rule aims to reduce potential bugs and unwanted behavior by ensuring that comparisons to null only match null, and not also undefined. As such, it will flag comparisons to null when using == and !=.

Examples of incorrect code for this rule:

Open in Playground

/*eslint no-eq-null: "error"*/

if (foo == null) {
  bar();
}

while (qux != null) {
  baz();
}
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Examples of correct code for this rule:

Open in Playground

/*eslint no-eq-null: "error"*/

if (foo === null) {
  bar();
}

while (qux !== null) {
  baz();
}
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Options

This rule has no options.

When Not To Use It

If you want to enforce type-checking operations in general, use the more powerful eqeqeq instead.

Compatibility

JSHint: This rule corresponds to eqnull rule of JSHint.

Version

This rule was introduced in ESLint v0.0.9.

Resources

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