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1899725695
* Type definitions for array.prototype.flatmap * array.prototype.flatmap: importing "/auto" extends the Array prototype
48 lines
2.4 KiB
TypeScript
48 lines
2.4 KiB
TypeScript
import flatMap = require("array.prototype.flatmap");
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import "array.prototype.flatmap/auto";
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import flatMapImpl = require("array.prototype.flatmap/implementation");
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import getPolyfill = require("array.prototype.flatmap/polyfill");
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import shim = require("array.prototype.flatmap/shim");
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// infers type of the output array from the return type of the callback
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flatMap(["foo"], word => word.split("")); // $ExpectType string[]
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flatMapImpl(["foo"], word => word.split("")); // $ExpectType string[]
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["foo"].flatMap(word => word.split("")); // $ExpectType string[]
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// infers the type of the value argument to the callback
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flatMap([1, 2], word => word.split("")); // $ExpectError
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flatMapImpl([1, 2], word => word.split("")); // $ExpectError
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[1, 2].flatMap(word => word.split("")); // $ExpectError
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// the callback must return an array
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flatMap([1, 2], word => word); // $ExpectError
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flatMapImpl([1, 2], word => word); // $ExpectError
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[1, 2].flatMap(word => word); // $ExpectError
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// the callback accepts an index argument
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flatMap(["foo"], (_, index) => [index]); // $ExpectType number[]
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flatMapImpl(["foo"], (_, index) => [index]); // $ExpectType number[]
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["foo"].flatMap((_, index) => [index]); // $ExpectType number[]
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// the callback accepts an argument that refers to the original array
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flatMap(["foo"], (_, __, input) => input); // $ExpectType string[]
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flatMapImpl(["foo"], (_, __, input) => input); // $ExpectType string[]
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["foo"].flatMap((_, __, input) => input); // $ExpectType string[]
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// the third argument is used as the calling context for the callback
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flatMap(["foo"], function() { return this.foo; }, { foo: [1, 2] }); // $ExpectType number[]
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flatMapImpl(["foo"], function() { return this.foo; }, { foo: [1, 2] }); // $ExpectType number[]
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["foo"].flatMap(function() { return this.foo; }, { foo: [1, 2] }); // $ExpectType number[]
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// assumes that value of `this` in callback is `undefined` by default (this is
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// accurate in strict mode)
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flatMap([1], function() { return [this]; }); // $ExpectType undefined[]
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flatMapImpl([1], function() { return [this]; }); // $ExpectType undefined[]
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[1].flatMap(function() { return [this]; }); // $ExpectType undefined[]
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// `getPolyfill` returns a flatMap implementation
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getPolyfill()(["foo"], word => word.split("")); // $ExpectType string[]
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// `shim` installs a flatMap implementation in `Array` prototype and returns it
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shim()(["foo"], word => word.split("")); // $ExpectType string[]
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