Filter array elements without mutation. Learn the syntax using an editable javascript example.
When to use it
Use this technique in collections, record processing and reusable transformations. Check the input types, any required imports, and whether the operation changes existing values or produces a new result.
Syntax
console.log(nums.filter(n => n % 2 === 0));
Parameters
Inspect the literals, variables and function arguments used in the example. Replace values with compatible javascript types before testing.
Returns / effect
Expected demonstration result: [2,4].
Expected output
[2,4]
Common mistake and fix
Avoid assuming collection order or mutation semantics without checking the language API.
Good practices
Keep the example small, check its documented output, then adapt it to your own project with validation and error handling.
Practice exercise
Try changing one input in the filter array elements without mutation example. Predict how the output changes, then compare with the reference output.
Compatibility: Confirm support in your installed language/runtime version; some examples need modern standard libraries.
Related concepts: collections, examples, syntax
Explain this code
Try a small exercise
Try changing one input in the filter array elements without mutation example. Predict how the output changes, then compare with the reference output.
Show a hint
Change a single literal or input first; compare the result before making more edits.
Show example solution
const nums = [1, 2, 3, 4]; console.log(nums.filter(n => n % 2 === 0));
Open permanent reference page ↗
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