90 lines
3.6 KiB
Markdown
90 lines
3.6 KiB
Markdown
# es-get-iterator <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
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[![dependency status][deps-svg]][deps-url]
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[![dev dependency status][dev-deps-svg]][dev-deps-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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Get an iterator for any JS language value. Works robustly across all environments, all versions.
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In modern engines, `value[Symbol.iterator]()` is sufficient to produce an iterator (an object with a `.next` method) for that object. However, older engines:
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- may lack `Symbol` support altogether
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- may have `Symbol.iterator` but not implement it on everything it should, like arguments objects
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- may have `Map` and `Set`, but a non-standard name for the iterator-producing method (`.iterator` or `['@@iterator']`, eg)
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- may be old versions of Firefox that produce values until they throw a StopIteration exception, rather than having iteration result objects
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- may be polyfilled/shimmed/shammed, with `es6-shim` or `core-js` or similar
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This library attempts to provide an abstraction over all that complexity!
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In node v13+, `exports` is used to provide a lean implementation that lacks all the complexity described above, in combination with the `browser` field so that bundlers will pick up the proper implementation.
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## Targeting browsers with Symbol support
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If you are targeting browsers that definitely all have Symbol support, then you can configure your bundler to replace `require('has-symbols')()` with a literal `true`, which should allow dead code elimination to reduce the size of the bundled code.
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### With `@rollup/plugin-replace`
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```js
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// rollup.config.js
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import replace from '@rollup/plugin-replace';
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export default {
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...
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plugins: [
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replace({
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"require('has-symbols')()": 'true',
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delimiters: ['', '']
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})
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]
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};
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```
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## Example
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```js
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var getIterator = require('es-get-iterator');
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var assert = require('assert');
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var iterator = getIterator('a 💩');
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assert.deepEqual(
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[iterator.next(), iterator.next(), iterator.next(), iterator.next()],
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[{ done: false, value: 'a' }, { done: false, value: ' ' }, { done: false, value: '💩' }, { done: true, value: undefined }]
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);
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var iterator = getIterator([1, 2]);
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assert.deepEqual(
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[iterator.next(), iterator.next(), iterator.next()],
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[{ done: false, value: 1 }, { done: false, value: 2 }, { done: true, value: undefined }]
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);
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var iterator = getIterator(new Set([1, 2]));
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assert.deepEqual(
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[iterator.next(), iterator.next(), iterator.next()],
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[{ done: false, value: 1 }, { done: false, value: 2 }, { done: true, value: undefined }]
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);
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var iterator = getIterator(new Map([[1, 2], [3, 4]]));
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assert.deepEqual(
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[iterator.next(), iterator.next(), iterator.next()],
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[{ done: false, value: [1, 2] }, { done: false, value: [3, 4] }, { done: true, value: undefined }]
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);
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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-get-iterator
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[npm-version-svg]: https://versionbadg.es/ljharb/es-get-iterator.svg
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[deps-svg]: https://david-dm.org/ljharb/es-get-iterator.svg
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[deps-url]: https://david-dm.org/ljharb/es-get-iterator
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[dev-deps-svg]: https://david-dm.org/ljharb/es-get-iterator/dev-status.svg
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[dev-deps-url]: https://david-dm.org/ljharb/es-get-iterator#info=devDependencies
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[npm-badge-png]: https://nodei.co/npm/es-get-iterator.png?downloads=true&stars=true
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[license-image]: https://img.shields.io/npm/l/es-get-iterator.svg
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[license-url]: LICENSE
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[downloads-image]: https://img.shields.io/npm/dm/es-get-iterator.svg
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[downloads-url]: https://npm-stat.com/charts.html?package=es-get-iterator
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