55 lines
962 B
JavaScript
55 lines
962 B
JavaScript
var once = require('once')
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var noop = function noop(){}
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module.exports = mapLimit
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function mapLimit(arr, limit, iterator, callback) {
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var complete = 0
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var aborted = false
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var results = []
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var queued = 0
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var l = arr.length
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var i = 0
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callback = once(callback || noop)
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if (typeof iterator !== 'function') throw new Error(
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'Iterator function must be passed as the third argument'
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)
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for (var r = 0; r < l; r++) {
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results[r] = null
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}
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flush()
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function flush() {
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if (complete === l)
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return callback(null, results)
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while (queued < limit) {
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if (aborted) break
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if (i === l) break
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push()
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}
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}
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function abort(err) {
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aborted = true
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return callback(err)
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}
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function push() {
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var idx = i++
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queued += 1
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iterator(arr[idx], function(err, result) {
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if (err) return abort(err)
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results[idx] = result
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complete += 1
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queued -= 1
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flush()
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})
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}
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}
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