isNonNullable()

isNonNullable<T>(value): value is NonNullable<T>

Checks if a value is not null or undefined.

💎 Why is this a Hidden Gem?

A powerful utility that filters out both null and undefined, narrowing types effectively.

note

Narrows T to NonNullable<T>. Uses loose equality (!= null) to check both.

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Type Parameters

T: T

The type of the value.

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Parameters

value: T

The value to check.

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Returns: value is NonNullable<T>

true if the value is not null or undefined, false otherwise.

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See Also

• isNil
• isNonNull

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Since

2.0.0

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Example

isNonNullable('hello');   // => true
isNonNullable(0);         // => true
isNonNullable(false);     // => true
isNonNullable(null);      // => false
isNonNullable(undefined); // => false

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How it works?

Type guard that checks if a value is not null or undefined.

Type Narrowing

Common Checks

Value	Result
0	true
''	true
false	true
NaN	true
null	false
undefined	false

Comparison

Guard	Excludes
isNonNull	null
isNonUndefined	undefined
isNonNullable	null AND undefined

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Use Cases

Filter missing values 📌

Remove null and undefined from arrays while narrowing types. Perfect for cleaning data lists before processing.

#filter#missing#nullable#narrowing#cleanup#validation

const items = [1, null, 2, undefined, 3];
const cleanItems = items.filter(isNonNullable); // Type is number[]

Chain with optional access

Combine with optional chaining for clean null-safe pipelines.

#chain#optional#chaining#pipeline#safe#narrowing

const userNames = users
  .map(u => u.profile?.displayName)
  .filter(isNonNullable);
// Type: string[] (no undefined)