| 1 | var random = require('./random')
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| 2 | var url = require('../url')
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| 3 |
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| 4 | /**
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| 5 | * Generate secure URL-friendly unique ID. Non-blocking version.
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| 6 | *
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| 7 | * By default, ID will have 21 symbols to have a collision probability similar
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| 8 | * to UUID v4.
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| 9 | *
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| 10 | * @param {number} [size=21] The number of symbols in ID.
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| 11 | *
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| 12 | * @return {Promise} Promise with random string.
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| 13 | *
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| 14 | * @example
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| 15 | * const nanoidAsync = require('nanoid/async')
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| 16 | * nanoidAsync.then(id => {
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| 17 | * model.id = id
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| 18 | * })
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| 19 | *
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| 20 | * @name async
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| 21 | * @function
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| 22 | */
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| 23 | module.exports = function (size) {
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| 24 | size = size || 21
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| 25 | return random(size).then(function (bytes) {
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| 26 | var id = ''
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| 27 | // Compact alternative for `for (var i = 0; i < size; i++)`
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| 28 | while (size--) {
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| 29 | // We can’t use bytes bigger than the alphabet. 63 is 00111111 bitmask.
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| 30 | // This mask reduces random byte 0-255 to 0-63 values.
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| 31 | // There is no need in `|| ''` and `* 1.6` hacks in here,
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| 32 | // because bitmask trim bytes exact to alphabet size.
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| 33 | id += url[bytes[size] & 63]
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| 34 | }
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| 35 | return id
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| 36 | })
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| 37 | }
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