Generate random string/characters in JavaScript
I want a 5 character string composed of characters picked randomly from the set [a-zA-Z0-9] .
What's the best way to do this with JavaScript?
我认为这会对你有用：
function makeid() {
var text = "";
var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
for (var i = 0; i < 5; i++)
text += possible.charAt(Math.floor(Math.random() * possible.length));
return text;
}
console.log(makeid());Math.random().toString(36).substring(7);
Math.random is bad for this kind of thing
Option 1
If you're able to do this server-side, just use the crypto module
var crypto = require("crypto");
var id = crypto.randomBytes(20).toString('hex');
// "bb5dc8842ca31d4603d6aa11448d1654"
The resulting string will be twice as long as the random bytes you generate; each byte encoded to hex is 2 characters. 20 bytes will be 40 characters of hex.
Option 2
If you have to do this client-side, perhaps try the uuid module
var uuid = require("uuid");
var id = uuid.v4();
// "110ec58a-a0f2-4ac4-8393-c866d813b8d1"
Option 3
If you have to do this client-side and you don't have to support old browsers, you can do it without dependencies
// dec2hex :: Integer -> String
function dec2hex (dec) {
return ('0' + dec.toString(16)).substr(-2)
}
// generateId :: Integer -> String
function generateId (len) {
var arr = new Uint8Array((len || 40) / 2)
window.crypto.getRandomValues(arr)
return Array.from(arr, dec2hex).join('')
}
console.log(generateId())
// "82defcf324571e70b0521d79cce2bf3fffccd69"
console.log(generateId(20))
// "c1a050a4cd1556948d41"