---
source: crates/biome_js_analyze/tests/spec_tests.rs
expression: invalid.js
---
# Input
```jsx

if (/*a*/ arr /*b*/ instanceof /*c*/ Array /*d*/) {}

const c = [1,2,3] instanceof globalThis.Array === b;

const d = foo.bar[2] instanceof window.Array

```

# Diagnostics
```
invalid.js:2:11 lint/suspicious/useIsArray  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Use Array.isArray() instead of instanceof Array.
  
  > 2 │ if (/*a*/ arr /*b*/ instanceof /*c*/ Array /*d*/) {}
      │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    3 │ 
    4 │ const c = [1,2,3] instanceof globalThis.Array === b;
  
  i instanceof Array returns false for array-like objects and arrays from other execution contexts.
  
  i Unsafe fix: Use Array.isArray() instead.
  
    1 1 │   
    2   │ - if·(/*a*/·arr·/*b*/·instanceof·/*c*/·Array·/*d*/)·{}
      2 │ + if·(/*a*/·Array.isArray(/*c*/·arr·/*b*/)·/*d*/)·{}
    3 3 │   
    4 4 │   const c = [1,2,3] instanceof globalThis.Array === b;
  

```

```
invalid.js:4:11 lint/suspicious/useIsArray  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Use Array.isArray() instead of instanceof Array.
  
    2 │ if (/*a*/ arr /*b*/ instanceof /*c*/ Array /*d*/) {}
    3 │ 
  > 4 │ const c = [1,2,3] instanceof globalThis.Array === b;
      │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    5 │ 
    6 │ const d = foo.bar[2] instanceof window.Array
  
  i instanceof Array returns false for array-like objects and arrays from other execution contexts.
  
  i Unsafe fix: Use Array.isArray() instead.
  
    2 2 │   if (/*a*/ arr /*b*/ instanceof /*c*/ Array /*d*/) {}
    3 3 │   
    4   │ - const·c·=·[1,2,3]·instanceof·globalThis.Array·===·b;
      4 │ + const·c·=·globalThis.Array.isArray([1,2,3])·===·b;
    5 5 │   
    6 6 │   const d = foo.bar[2] instanceof window.Array
  

```

```
invalid.js:6:11 lint/suspicious/useIsArray  FIXABLE  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ! Use Array.isArray() instead of instanceof Array.
  
    4 │ const c = [1,2,3] instanceof globalThis.Array === b;
    5 │ 
  > 6 │ const d = foo.bar[2] instanceof window.Array
      │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    7 │ 
  
  i instanceof Array returns false for array-like objects and arrays from other execution contexts.
  
  i Unsafe fix: Use Array.isArray() instead.
  
    4 4 │   const c = [1,2,3] instanceof globalThis.Array === b;
    5 5 │   
    6   │ - const·d·=·foo.bar[2]·instanceof·window.Array
      6 │ + const·d·=·window.Array.isArray(foo.bar[2])
    7 7 │   
  

```