如果你只想允许特定的字符，你也可以这样做:

function randomString(length, chars) {
    var result = '';
    for (var i = length; i > 0; --i) result += chars[Math.floor(Math.random() * chars.length)];
    return result;
}
var rString = randomString(32, '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ');

下面是一个演示的jsfiddle: http://jsfiddle.net/wSQBx/

另一种方法是使用一个特殊的字符串，告诉函数使用什么类型的字符。你可以这样做:

function randomString(length, chars) {
    var mask = '';
    if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
    if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
    if (chars.indexOf('#') > -1) mask += '0123456789';
    if (chars.indexOf('!') > -1) mask += '~`!@#$%^&*()_+-={}[]:";\'<>?,./|\\';
    var result = '';
    for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() * mask.length)];
    return result;
}

console.log(randomString(16, 'aA'));
console.log(randomString(32, '#aA'));
console.log(randomString(64, '#A!'));

小提琴:http://jsfiddle.net/wSQBx/2/

或者，像下面描述的那样使用base36方法，你可以这样做:

function randomString(length) {
    return Math.round((Math.pow(36, length + 1) - Math.random() * Math.pow(36, length))).toString(36).slice(1);
}

这是一个简单的代码来生成随机字符串字母。 看看这段代码是如何工作的。 去(lenthOfStringToPrint);-使用此函数生成最终字符串。

var letters = {
  1: ["q","w","e","r","t","y","u","i","o","p","a","s","d","f","g","h","j","k","l","z","x","c","v","b","n","m"],
  2: ["Q","W","E","R","T","Y","U","I","O","P","A","S","D","F","G","H","J","K","L","Z","X","C","V","B","N","M"]
},i,letter,final="";
random = (max,min) => {
  return Math.floor(Math.random()*(max-min+1)+min);
}
function go(length) {
  final="",letter="";
  for (i=1; i<=length; i++){
    letter = letters[random(0,3)][random(0,25)];
    final+=letter;
  }
  return final;
}

当我看到这个问题时，我想到了我必须生成uuid的时候。我不能把代码的功劳，因为我确信我在stackoverflow上找到了它。如果你不想在字符串中使用破折号，那就去掉破折号。函数如下:

function generateUUID() {
    var d = new Date().getTime();
    var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g,function(c) {
        var r = (d + Math.random()*16)%16 | 0;
        d = Math.floor(d/16);
        return (c=='x' ? r : (r&0x7|0x8)).toString(16);
    });
    return uuid.toUpperCase();
}

小提琴:http://jsfiddle.net/nlviands/fNPvf/11227/

我使用@Nimphious优秀的第二种方法，发现偶尔返回的字符串是数字-而不是字母数字。 我使用的解决方案是测试使用!isNaN，并再次使用递归调用该函数。 何苦呢?我使用这个函数来创建对象键，如果所有的键都是字母数字，那么所有的键都可以正常排序，但如果你使用 数字作为键与字母数字(字符串)混合在一起循环遍历对象将产生与原始顺序不同的顺序。

function newRandomString(length, chars) {
  var mask = '';
  if (chars.indexOf('a') > -1) mask += 'abcdefghijklmnopqrstuvwxyz';
  if (chars.indexOf('A') > -1) mask += 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
  if (chars.indexOf('#') > -1) mask += '0123456789';
  if (chars.indexOf('$') > -1) mask += '0123456789';

  var result = '';
  for (var i = length; i > 0; --i) result += mask[Math.floor(Math.random() * 
  mask.length)];
  /*    
        we need a string not a number !isNaN(result)) will return true if '1234' or '3E77'
        because if we're looping through object keys (created by newRandomString()) and 
        a number is used and all the other keys are strings then the number will 
        be first even if it was the 2nd or third key in object
  */
  //use recursion to try again
  if(!isNaN(result)){
    console.log('found a number....:'+result);
    return newRandomString(length, chars)
  }else{
    return result;
  }
};

var i=0;
while (i < 1000) {
  var a = newRandomString(4, '#$aA');
  console.log(i+' - '+a);
  //now we're using recursion this won't occur
  if(!isNaN(a)){
    console.log('=============='+i+' - '+a);
  }
  i++;
}

console.log('3E77:'+!isNaN('3E77'));//true
console.log('1234:'+!isNaN('1234'));//true
console.log('ab34:'+!isNaN('ab34'));//false

32个字符:

for(var c = ''; c.length < 32;) c += Math.random().toString(36).substr(2, 1)

var randomString = function(length) {
  var str = '';
  var chars ='0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz'.split(
      '');
  var charsLen = chars.length;
  if (!length) {
    length = ~~(Math.random() * charsLen);
  }
  for (var i = 0; i < length; i++) {
    str += chars[~~(Math.random() * charsLen)];
  }
  return str;
};