defined

@nick/is/defined

isDefined

Signature

function isDefined<T>(it: T | undefined): it is T;

Checks if a value is not undefined.

Parameters

Name	Info
it	The value to check.

Returns

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

Category

Primitives

Examples

import { isDefined } from "jsr:@nick/is/defined";

isDefined(null); // true
isDefined(undefined); // false
isDefined(0); // true
isDefined(void 0); // false
isDefined(""); // true

import { isDefined } from "jsr:@nick/is/defined";

let value: number | undefined;
if (isDefined(value)) {
  value += 1;
  // ^? let value: number
} else {
  value;
  // ^? let value: undefined
  value = 0;
  // ^? let value: number | undefined
}