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/isNil.md.
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    isNil es-toolkit

    Checks if a value is null or undefined.

    const result = isNil(value);

    Usage

    isNil(value)

    Use isNil when you want to check if a value is null or undefined.

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

// null or undefined values
console.log(isNil(null)); // true
console.log(isNil(undefined)); // true

// Other values
console.log(isNil(0)); // false
console.log(isNil('')); // false
console.log(isNil(false)); // false
console.log(isNil([])); // false
console.log(isNil({})); // false

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

    function processValue(value: string | null | undefined) {
  if (isNil(value)) {
    // value is now narrowed to null | undefined
    console.log('Value is empty');
  } else {
    // value is narrowed to string
    console.log(value.toUpperCase());
  }
}

    Parameters

    valueunknownrequired

    The value to check if it's null or undefined.

    Returns

    Returns true if the value is null or undefined, false otherwise.

    value is null | undefined
    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.