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 to not just a null, but also an undefined value.

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

Rule Details

The no-eq-null rule aims reduce potential bug 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:

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

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

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

Examples of correct code for this rule:

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

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

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

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

• Rule source
• Tests source