For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt, and this page is available as Markdown at /reference/predicate/isNull.md.
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    isNull es-toolkit

    Checks if a value is null.

    const result = isNull(value);

    Usage

    isNull(value)

    Use isNull when you want to check if a value is exactly null. It uses strict equality (===) to recognize only null and not undefined.

    import { isNull } from 'es-toolkit/predicate';

// null value
console.log(isNull(null)); // true

// Non-null values
console.log(isNull(undefined)); // false
console.log(isNull(0)); // false
console.log(isNull('')); // false
console.log(isNull(false)); // false
console.log(isNull([])); // false
console.log(isNull({})); // false

    It can also be used as a type guard in TypeScript.

    function processValue(value: string | null | undefined) {
  if (isNull(value)) {
    // value is now narrowed to null
    console.log('Value is null');
  } else {
    // value is narrowed to string | undefined
    console.log('Value is not null:', value);
  }
}

    isNull is different from isNil in that it treats undefined as false.

    import { isNil, isNull } from 'es-toolkit/predicate';

console.log(isNull(undefined)); // false
console.log(isNil(undefined)); // true

    Parameters

    valueunknownrequired

    The value to check if it's null.

    Returns

    Returns true if the value is null, false otherwise.

    value is null
    Source: es-toolkit

    Re-exported verbatim from es-toolkit. Implementation, edge cases, and performance behavior are owned upstream. This page mirrors the documentation at the pinned version; the linked source is authoritative.