35 lines
927 B
JavaScript
35 lines
927 B
JavaScript
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var random = require('./random')
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var url = require('./url')
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/**
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* Generate secure URL-friendly unique ID.
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*
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* By default, ID will have 21 symbols to have a collision probability similar
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* to UUID v4.
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*
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* @param {number} [size=21] The number of symbols in ID.
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*
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* @return {string} Random string.
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*
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* @example
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* const nanoid = require('nanoid')
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* model.id = nanoid() //=> "Uakgb_J5m9g-0JDMbcJqL"
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*
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* @name nanoid
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* @function
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*/
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module.exports = function (size) {
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size = size || 21
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var bytes = random(size)
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var id = ''
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// Compact alternative for `for (var i = 0; i < size; i++)`
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while (size--) {
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// We can’t use bytes bigger than the alphabet. 63 is 00111111 bitmask.
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// This mask reduces random byte 0-255 to 0-63 values.
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// There is no need in `|| ''` and `* 1.6` hacks in here,
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// because bitmask trim bytes exact to alphabet size.
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id += url[bytes[size] & 63]
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}
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return id
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}
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