get-intrinsic

What is get-intrinsic?

The get-intrinsic package is a utility that allows you to safely obtain references to ECMAScript language intrinsics without relying on the global namespace, which can be altered by other code. It helps in writing robust code that doesn't get affected by modifications to the global objects or functions.

What are get-intrinsic's main functionalities?

Getting intrinsic values

This feature allows you to get the original intrinsic value of Array.prototype.push, which can then be used to push elements to arrays without relying on Array.prototype.push being unmodified.

var getIntrinsic = require('get-intrinsic');
var ArrayPrototypePush = getIntrinsic('%Array.prototype.push%');
var anArray = [1, 2, 3];
ArrayPrototypePush(anArray, 4); // anArray becomes [1, 2, 3, 4]

Accessing deep intrinsics

This feature allows you to access deep intrinsic properties like Object.prototype.hasOwnProperty, which can be used to check for properties without relying on the original method being unaltered.

var getIntrinsic = require('get-intrinsic');
var hasOwn = getIntrinsic('%Object.prototype.hasOwnProperty%');
var hasDuck = hasOwn.call({ duck: 'quack' }, 'duck'); // hasDuck is true

Ensuring unmodified constructors

This feature allows you to use the original Array constructor to create new arrays, ensuring that the constructor has not been modified in the global scope.

var getIntrinsic = require('get-intrinsic');
var ArrayConstructor = getIntrinsic('%Array%');
var myArray = new ArrayConstructor(1, 2, 3); // myArray is [1, 2, 3]

Other packages similar to get-intrinsic

es-abstract

The es-abstract package provides methods to access the ECMAScript abstract operations. It is similar to get-intrinsic in that it allows access to fundamental ECMAScript operations, but it focuses more on the abstract operations rather than the intrinsic objects and methods.

es5-shim

The es5-shim package provides shims for legacy JavaScript engines to support ECMAScript 5 features. While it does not directly provide a way to access intrinsics, it ensures that the standard methods and objects behave as expected in older environments, which is somewhat related to the goal of get-intrinsic.

core-js

Core-js is a modular standard library for JavaScript, which includes polyfills for ECMAScript features. It provides a stable environment for using modern JavaScript features in older browsers, similar to get-intrinsic's goal of providing stable references to intrinsic objects and methods.

README

get-intrinsic

Get and robustly cache all JS language-level intrinsics at first require time.

See the syntax described in the JS spec for reference.

Example

var GetIntrinsic = require('get-intrinsic');
var assert = require('assert');

// static methods
assert.equal(GetIntrinsic('%Math.pow%'), Math.pow);
assert.equal(Math.pow(2, 3), 8);
assert.equal(GetIntrinsic('%Math.pow%')(2, 3), 8);
delete Math.pow;
assert.equal(GetIntrinsic('%Math.pow%')(2, 3), 8);

// instance methods
var arr = [1];
assert.equal(GetIntrinsic('%Array.prototype.push%'), Array.prototype.push);
assert.deepEqual(arr, [1]);

arr.push(2);
assert.deepEqual(arr, [1, 2]);

GetIntrinsic('%Array.prototype.push%').call(arr, 3);
assert.deepEqual(arr, [1, 2, 3]);

delete Array.prototype.push;
GetIntrinsic('%Array.prototype.push%').call(arr, 4);
assert.deepEqual(arr, [1, 2, 3, 4]);

// missing features
delete JSON.parse; // to simulate a real intrinsic that is missing in the environment
assert.throws(() => GetIntrinsic('%JSON.parse%'));
assert.equal(undefined, GetIntrinsic('%JSON.parse%', true));

Tests

Simply clone the repo, npm install, and run npm test

Security

Please email @ljharb or see https://tidelift.com/security if you have a potential security vulnerability to report.