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47 lines
1.2 KiB
47 lines
1.2 KiB
var assert = require("assert")
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var dezalgoify = require("dezalgo")
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module.exports = some
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/**
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* short-circuited async Array.prototype.some implementation
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*
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* Serially evaluates a list of values from a JS array or arraylike
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* against an asynchronous predicate, terminating on the first truthy
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* value. If the predicate encounters an error, pass it to the completion
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* callback. Otherwise, pass the truthy value passed by the predicate, or
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* `false` if no truthy value was passed.
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*/
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function some (list, test, cb) {
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assert("length" in list, "array must be arraylike")
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assert.equal(typeof test, "function", "predicate must be callable")
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assert.equal(typeof cb, "function", "callback must be callable")
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var array = slice(list)
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, index = 0
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, length = array.length
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, hecomes = dezalgoify(cb)
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map()
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function map () {
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if (index >= length) return hecomes(null, false)
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test(array[index], reduce)
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}
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function reduce (er, result) {
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if (er) return hecomes(er, false)
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if (result) return hecomes(null, result)
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index++
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map()
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}
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}
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// Array.prototype.slice on arguments arraylike is expensive
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function slice(args) {
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var l = args.length, a = [], i
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for (i = 0; i < l; i++) a[i] = args[i]
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return a
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}
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