projects / pve-eslint.git / blame
| Commit | Line | Data |
|---|---|---|
| eb39fafa DC |
1 | # Disallow Null Comparisons (no-eq-null) |
| 2 | ||
| 3 | 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. | |
| 4 | ||
| 5 | ```js | |
| 6 | if (foo == null) { | |
| 7 | bar(); | |
| 8 | } | |
| 9 | ``` | |
| 10 | ||
| 11 | ## Rule Details | |
| 12 | ||
| 13 | 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 `!=`. | |
| 14 | ||
| 15 | Examples of **incorrect** code for this rule: | |
| 16 | ||
| 17 | ```js | |
| 18 | /*eslint no-eq-null: "error"*/ | |
| 19 | ||
| 20 | if (foo == null) { | |
| 21 | bar(); | |
| 22 | } | |
| 23 | ||
| 24 | while (qux != null) { | |
| 25 | baz(); | |
| 26 | } | |
| 27 | ``` | |
| 28 | ||
| 29 | Examples of **correct** code for this rule: | |
| 30 | ||
| 31 | ```js | |
| 32 | /*eslint no-eq-null: "error"*/ | |
| 33 | ||
| 34 | if (foo === null) { | |
| 35 | bar(); | |
| 36 | } | |
| 37 | ||
| 38 | while (qux !== null) { | |
| 39 | baz(); | |
| 40 | } | |
| 41 | ``` | |
| 609c276f TL |
42 | |
| 43 | ## Compatibility | |
| 44 | ||
| 45 | * **JSHint**: This rule corresponds to `eqnull` rule of JSHint. | |
| 46 | ||
| 47 | ## When Not To Use It | |
| 48 | ||
| 49 | If you want to enforce type-checking operations in general, use the more powerful [eqeqeq](./eqeqeq) instead. |