isFunctionLike
function isFunctionLike(value: unknown): value is Function;
The cheap test — typeof value === "function" — which is what you want before calling something. isFunction is the stricter reading of the same question.
isX and nonX answer a question and never interrupt control flow; requireX and requireNonX hand the value back or throw. The scheme is explained in Validation conventions.
Parameters
Parameter | Type | Description |
|---|---|---|
|
| The value to check. |
Returns
boolean — true when the value is callable; otherwise false.
In TypeScript the guard narrows value to Function inside the branch.
Examples
What passes and what does not
isFunctionLike(function () {}); // => true
isFunctionLike(Math.max); // => true
isFunctionLike(null); // => false
isFunctionLike({}); // => false
isFunctionLike("fn"); // => false
See also
Source
23 September 2026
This documentation was generated with AI (Claude) from the library's source code.