useIsArray
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Diagnostic Category: lint/suspicious/useIsArray
Since: v1.0.0
Sources:
- Same as:
unicorn/no-instanceof-array
Use Array.isArray()
instead of instanceof Array
.
In JavaScript some array-like objects such as arguments are not instances of the Array
class. ///
Moreover, the global Array
class can be different between two execution contexts.
For instance, two frames in a web browser have a distinct Array
class.
Passing arrays across these contexts, results in arrays that are not instances of the contextual global Array
class.
To avoid these issues, use Array.isArray()
instead of instanceof Array
.
See the MDN docs for more details.
Examples
Section titled ExamplesInvalid
Section titled Invalidcode-block.js:2:5 lint/suspicious/useIsArray FIXABLE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
✖ Use Array.isArray() instead of instanceof Array.
1 │ const xs = [];
> 2 │ if (xs instanceof Array) {}
│ ^^^^^^^^^^^^^^^^^^^
3 │
ℹ instanceof Array returns false for array-like objects and arrays from other execution contexts.
ℹ Unsafe fix: Use Array.isArray() instead.
1 1 │ const xs = [];
2 │ - if·(xs·instanceof·Array)·{}
2 │ + if·(Array.isArray(xs))·{}
3 3 │