identity()

identity<T>(value): T

Returns the first argument it receives.

DEPRECATED

Use an inline arrow function (x) => x instead.

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Type Parameters

T: T

The type of the value.

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Parameters

value: T

Any value.

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Returns: T

The value.

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Since

2.0.0

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Also known as

identity (Lodash, es-toolkit, Remeda, Ramda, Effect) · ❌ (Radashi, Modern Dash, Antfu)

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Example

// ❌ Deprecated approach
[1, 2, 3].filter(identity);

// ✅ Recommended approach
[1, 2, 3].filter(x => x);
// Or simply
[1, 2, 3].filter(Boolean);

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How it works?

Returns the first argument it receives. Deprecated: Use an inline arrow function (x) => x instead.

Native Equivalent

// ❌ arr.filter(identity)
// ✅ arr.filter(x => x)
// ✅ arr.filter(Boolean)

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Use Cases

Pass-through function 📌

Return value unchanged.

#identity#passthrough#noop#function

const fn = (x: T) => x;
// Or for filtering truthy:
[1, 0, 2, null].filter(Boolean);  // [1, 2]

Default transformer

Use as default when no transform needed.

#default#transformer#callback#optional

function process<T>(items: T[], transform = (x: T) => x) {
  return items.map(transform);
}