生成包含aA zZ和0-9字符集合的随机字符串。只需使用长度参数调用此函数。

所以要回答这个问题：generateRandomString（5）

generateRandomString(length){
    let result = "", seeds

    for(let i = 0; i < length - 1; i++){
        //Generate seeds array, that will be the bag from where randomly select generated char
        seeds = [
            Math.floor(Math.random() * 10) + 48,
            Math.floor(Math.random() * 25) + 65,
            Math.floor(Math.random() * 25) + 97
        ]
        
        //Choise randomly from seeds, convert to char and append to result
        result += String.fromCharCode(seeds[Math.floor(Math.random() * 3)])
    }

    return result
}

生成不带数字的字符串的版本：

generateRandomString(length){
    let result = "", seeds

    for(let i = 0; i < length - 1; i++){
        seeds = [
            Math.floor(Math.random() * 25) + 65,
            Math.floor(Math.random() * 25) + 97
        ]
        result += String.fromCharCode(seeds[Math.floor(Math.random() * 2)])
    }

    return result
}

function generate(length) {
  var letters = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z","0","1","2","3","4","5","6","7","8","9"];
  var IDtext = "";
  var i = 0;
  while (i < length) {
    var letterIndex = Math.floor(Math.random() * letters.length);
    var letter = letters[letterIndex];
    IDtext = IDtext + letter;
    i++;
  }
  console.log(IDtext)
}

一行使用地图，可以完全控制长度和字符。

const rnd = (len, chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789') => [...Array(len)].map(() => chars.charAt(Math.floor(Math.random() * chars.length))).join('')

console.log(rnd(12))

这是我创建的方法。它将创建一个包含大小写字符的字符串。此外，我还包含了将创建字母数字字符串的函数。

工作示例：http://jsfiddle.net/greatbigmassive/vhsxs/（仅限alpha）http://jsfiddle.net/greatbigmassive/PJwg8/（字母数字）

function randString(x){
    var s = "";
    while(s.length<x&&x>0){
        var r = Math.random();
        s+= String.fromCharCode(Math.floor(r*26) + (r>0.5?97:65));
    }
    return s;
}

2015年7月升级这做了同样的事情，但更有意义，包括所有字母。

var s = "";
while(s.length<x&&x>0){
    v = Math.random()<0.5?32:0;
    s += String.fromCharCode(Math.round(Math.random()*((122-v)-(97-v))+(97-v)));
}

下面这个怎么样。。。这将产生真正随机的值：

function getRandomStrings(length) {
  const value = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  const randoms = [];
  for(let i=0; i < length; i++) {
     randoms.push(value[Math.floor(Math.random()*value.length)]);
  }
  return randoms.join('');
}

但如果您在ES6中寻找一个较短的语法：

const getRandomStrings = length => Math.random().toString(36).substr(-length);

这是我用过的。这是一对夫妇的组合。我在循环中使用它，它生成的每个ID都是唯一的。它可能不是5个字符，但它保证是唯一的。

var newId =
    "randomid_" +
    (Math.random() / +new Date()).toString(36).replace(/[^a-z]+/g, '');