67 lines
3.4 KiB
Markdown
67 lines
3.4 KiB
Markdown
# iterate-value <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
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[![Build Status][travis-svg]][travis-url]
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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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Iterate any iterable JS value. Works robustly in all environments, all versions.
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In modern engines, `[...value]` or `Array.from(value)` or `for (const item of value) { }` are sufficient to iterate an iterable value (an object with a `Symbol.iterator` method). However, older engines:
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- may lack `Symbol`, array spread, or `for..of` 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) and no syntax to support it
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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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If called with a single value, it will return an array of the yielded values. If also called with a callback function, it will instead call that callback once for each yielded value.
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In node v13+, `exports` is used by the `es-get-iterator` dependency 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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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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## Example
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```js
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var iterate = require('iterate-value');
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var assert = require('assert');
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assert.deepEqual(iterate('a 💩'), ['a', ' ', '💩']);
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assert.deepEqual(iterate([1, 2]), [1, 2]);
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assert.deepEqual(iterate(new Set([1, 2])), [1, 2]);
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assert.deepEqual(iterate(new Map([[1, 2], [3, 4]])), [[1, 2], [3, 4]]);
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function assertWithCallback(iterable, expected) {
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var values = [];
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var callback = function (x) { values.push(x); };
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iterate(iterable, callback);
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assert.deepEqual(values, expected);
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}
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assertWithCallback('a 💩', ['a', ' ', '💩']);
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assertWithCallback([1, 2], [1, 2]);
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assertWithCallback(new Set([1, 2]), [1, 2]);
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assertWithCallback(new Map([[1, 2], [3, 4]]), [[1, 2], [3, 4]]);
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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/iterate-value
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[npm-version-svg]: http://versionbadg.es/ljharb/iterate-value.svg
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[travis-svg]: https://travis-ci.org/ljharb/iterate-value.svg
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[travis-url]: https://travis-ci.org/ljharb/iterate-value
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[deps-svg]: https://david-dm.org/ljharb/iterate-value.svg
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[deps-url]: https://david-dm.org/ljharb/iterate-value
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[dev-deps-svg]: https://david-dm.org/ljharb/iterate-value/dev-status.svg
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[dev-deps-url]: https://david-dm.org/ljharb/iterate-value#info=devDependencies
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[npm-badge-png]: https://nodei.co/npm/iterate-value.png?downloads=true&stars=true
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[license-image]: http://img.shields.io/npm/l/iterate-value.svg
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[license-url]: LICENSE
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[downloads-image]: http://img.shields.io/npm/dm/iterate-value.svg
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[downloads-url]: http://npm-stat.com/charts.html?package=iterate-value
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