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68 lines
3.0 KiB
Markdown
68 lines
3.0 KiB
Markdown
# es-abstract-get <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
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[![github actions][actions-image]][actions-url]
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[![coverage][codecov-image]][codecov-url]
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[![License][license-image]][license-url]
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[![Downloads][downloads-image]][downloads-url]
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[![npm badge][npm-badge-png]][package-url]
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The ECMAScript “getting properties” abstract operations — [`Get`][Get], [`GetV`][GetV], and [`GetMethod`][GetMethod] — plus the [`isPropertyKey`][isPropertyKey] helper they share, with TypeScript types.
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## Motivation
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These operations are also available in [`es-abstract`][es-abstract],
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but `es-abstract` ships every abstract operation for every spec edition,
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so depending on it to use one or two of them pulls in a very large dependency graph.
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These three operations (and `isPropertyKey`) historically never differ between spec editions,
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so they’re split out here:
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a package that only needs `Get`, `GetV`, `GetMethod`, or `isPropertyKey` can depend on this instead and get a far smaller install.
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Each operation is its own entry point - there is intentionally no main (`.`) export - so you only pay for what you import.
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## Example
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```js
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var Get = require('es-abstract-get/Get');
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var GetV = require('es-abstract-get/GetV');
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var GetMethod = require('es-abstract-get/GetMethod');
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var isPropertyKey = require('es-abstract-get/isPropertyKey');
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var assert = require('assert');
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// Get(O, P): O must be an Object
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assert.equal(Get({ a: 1 }, 'a'), 1);
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// GetV(V, P): V may be a primitive (it is coerced to an object for the lookup,
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// but the original value is the receiver)
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assert.equal(GetV('abc', 'length'), 3);
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// GetMethod(O, P): returns undefined for null/undefined, throws if not callable
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assert.equal(GetMethod({}, 'toString'), Object.prototype.toString);
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assert.equal(GetMethod({ a: null }, 'a'), undefined);
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// isPropertyKey(argument): true for strings and symbols
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assert.equal(isPropertyKey('a'), true);
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assert.equal(isPropertyKey(Symbol.iterator), true);
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assert.equal(isPropertyKey(1), false);
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```
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## Tests
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Simply clone the repo, `npm install`, and run `npm test`
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[package-url]: https://npmjs.org/package/es-abstract-get
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[npm-version-svg]: https://versionbadg.es/ljharb/es-abstract-get.svg
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[npm-badge-png]: https://nodei.co/npm/es-abstract-get.png?downloads=true&stars=true
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[license-image]: https://img.shields.io/npm/l/es-abstract-get.svg
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[license-url]: LICENSE
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[downloads-image]: https://img.shields.io/npm/dm/es-abstract-get.svg
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[downloads-url]: https://npm-stat.com/charts.html?package=es-abstract-get
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[codecov-image]: https://codecov.io/gh/ljharb/es-abstract-get/branch/main/graphs/badge.svg
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[codecov-url]: https://app.codecov.io/gh/ljharb/es-abstract-get/
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[actions-image]: https://img.shields.io/github/check-runs/ljharb/es-abstract-get/main
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[actions-url]: https://github.com/ljharb/es-abstract-get/actions
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[es-abstract]: https://npmjs.org/package/es-abstract
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[Get]: https://tc39.es/ecma262/#sec-get-o-p
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[GetV]: https://tc39.es/ecma262/#sec-getv
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[GetMethod]: https://tc39.es/ecma262/#sec-getmethod
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[isPropertyKey]: https://tc39.es/ecma262/#sec-ispropertykey
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