Module index

Core utility types and type guards.

import {
  isDefined,
  isFunction,
  isError,
  isPromise,
  isIterable,
  isAsyncIterable
} from '@metreeca/core';

if (isDefined(value)) {
  return value.property; // value is narrowed to exclude undefined and null
}

if (isFunction(value)) {
  value(); // value is narrowed to Function type
}

if (isError(value)) {
  console.error(value.message); // value is narrowed to Error
}

if (isPromise(value)) {
  await value; // value is narrowed to Promise type
}

if (isIterable(value)) {
  for (const item of value) { // value implements iterable protocol
    process(item);
  }
}

if (isAsyncIterable(value)) {
  for await (const item of value) { // value implements async iterable protocol
    await process(item);
  }
}

Type Aliases

Identifier: ECMAScript Identifier.
Some: A value or a readonly array of values.
Lazy: A value or a function returning a value.

Functions

isIdentifier: Checks if a value is a valid Identifier.
isDefined: Checks if a value is not undefined or null.
isSymbol: Checks if a value is a symbol.
isFunction: Checks if a value is a function.
isError: Checks if a value is an Error instance.
isRegExp: Checks if a value is a RegExp instance.
isDate: Checks if a value is a Date instance.
isPromise: Checks if a value is a promise.
isIterable: Checks if a value is iterable.
isAsyncIterable: Checks if a value is async iterable.

Module index

Type Aliases

Functions

Settings

On This Page