38 lines
1.2 KiB
JavaScript
38 lines
1.2 KiB
JavaScript
// This file replaces `async/index.js` in bundlers like webpack or Rollup,
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// according to `browser` config in `package.json`.
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var crypto = self.crypto || self.msCrypto
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// This alphabet uses a-z A-Z 0-9 _- symbols.
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// Symbols are generated for smaller size.
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// -_zyxwvutsrqponmlkjihgfedcba9876543210ZYXWVUTSRQPONMLKJIHGFEDCBA
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var url = '-_'
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// Loop from 36 to 0 (from z to a and 9 to 0 in Base36).
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var i = 36
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while (i--) {
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// 36 is radix. Number.prototype.toString(36) returns number
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// in Base36 representation. Base36 is like hex, but it uses 0–9 and a-z.
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url += i.toString(36)
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}
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// Loop from 36 to 10 (from Z to A in Base36).
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i = 36
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while (i-- - 10) {
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url += i.toString(36).toUpperCase()
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}
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module.exports = function (size) {
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var id = ''
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var bytes = crypto.getRandomValues(new Uint8Array(size || 21))
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i = size || 21
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// Compact alternative for `for (var i = 0; i < size; i++)`
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while (i--) {
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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[i] & 63]
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}
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return Promise.resolve(id)
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}
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