38 lines
1.2 KiB
JavaScript
38 lines
1.2 KiB
JavaScript
|
// This file replaces `async/index.js` in bundlers like webpack or Rollup,
|
|||
|
|
// according to `browser` config in `package.json`.
|
|||
|
|
|
|||
|
|
var crypto = self.crypto || self.msCrypto
|
|||
|
|
|
|||
|
|
// This alphabet uses a-z A-Z 0-9 _- symbols.
|
|||
|
|
// Symbols are generated for smaller size.
|
|||
|
|
// -_zyxwvutsrqponmlkjihgfedcba9876543210ZYXWVUTSRQPONMLKJIHGFEDCBA
|
|||
|
|
var url = '-_'
|
|||
|
|
// Loop from 36 to 0 (from z to a and 9 to 0 in Base36).
|
|||
|
|
var i = 36
|
|||
|
|
while (i--) {
|
|||
|
|
// 36 is radix. Number.prototype.toString(36) returns number
|
|||
|
|
// in Base36 representation. Base36 is like hex, but it uses 0–9 and a-z.
|
|||
|
|
url += i.toString(36)
|
|||
|
|
}
|
|||
|
|
// Loop from 36 to 10 (from Z to A in Base36).
|
|||
|
|
i = 36
|
|||
|
|
while (i-- - 10) {
|
|||
|
|
url += i.toString(36).toUpperCase()
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
module.exports = function (size) {
|
|||
|
|
var id = ''
|
|||
|
|
var bytes = crypto.getRandomValues(new Uint8Array(size || 21))
|
|||
|
|
i = size || 21
|
|||
|
|
|
|||
|
|
// Compact alternative for `for (var i = 0; i < size; i++)`
|
|||
|
|
while (i--) {
|
|||
|
|
// We can’t use bytes bigger than the alphabet. 63 is 00111111 bitmask.
|
|||
|
|
// This mask reduces random byte 0-255 to 0-63 values.
|
|||
|
|
// There is no need in `|| ''` and `* 1.6` hacks in here,
|
|||
|
|
// because bitmask trim bytes exact to alphabet size.
|
|||
|
|
id += url[bytes[i] & 63]
|
|||
|
|
}
|
|||
|
|
return Promise.resolve(id)
|
|||
|
|
}
|