Question

如何使用Javascript中的以下条件生成随机数

字符串应包含[a-z]
字符串应包含[A-Z]
字符串应至少包含[0-9]

注意：由于遗传原因，我不想使用任何JS库

我尝试了下面的代码，但它不符合上述条件，例如有时它根本不包含数字....

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';
    var result = '';
    for (var i = length; i > 0; --i) result += mask[Math.round(Math.random() * (mask.length - 1))];
    return result;
}
document.write(randomString(12, 'aA#'));

有没有更好的方法呢？

Answer 1

以下是如何做到这一点：生成一个代表你的标准的数组，将其洗牌并填充数组。

示例：

function makeRandomString(criteria) {

  // From http://stackoverflow.com/q/2450954/3371119
  function shuffle(array) {
      var currentIndex = array.length,
        temporaryValue, randomIndex;

      // While there remain elements to shuffle...
      while (0 !== currentIndex) {

        // Pick a remaining element...
        randomIndex = Math.floor(Math.random() * currentIndex);
        currentIndex -= 1;

        // And swap it with the current element.
        temporaryValue = array[currentIndex];
        array[currentIndex] = array[randomIndex];
        array[randomIndex] = temporaryValue;
      }

      return array;
  }
  // Choose a random character from a string
  function chooseRandom(str) {
      return str[Math.floor(Math.random() * str.length)];
  }
  // Shuffle the criteria
  shuffle(criteria);
  var result = "";
  // Build the resulting string by choosing a random character from each part
  for (var i = 0; i < criteria.length; ++i) result += chooseRandom(criteria[i]);
  return result;
}

使用示例：

// Some constants explaining the criteria
var lowercase = "abcdefghijklmnopqrstuvwxyz";
var uppercase = lowercase.toUpperCase();
var numbers = "0123456789";
// Note: if you don't like typing all that, change the names to L, N, and U
var criteria = [lowercase, lowercase, lowercase, lowercase, // 4 lowercase
                numbers, numbers, numbers, numbers, // 4 numbers
                uppercase, uppercase, uppercase, uppercase // 4 uppercase
               ];
console.log(makeRandomString(criteria));

甚至更好（更少打字）：

function repeat(elem, n) {
  var result = [];
  for (var i = 0; i < n; ++i) result.push(elem);
  return result;
}

var criteria = repeat(lowercase, 4)
              .concat(repeat(uppercase, 4))
              .concat(repeat(numbers, 4));
console.log(makeRandomString(criteria));

Answer 2

这是我的解决方案：

var text = " ";
var numChars = "0123456789";
var upCaseChars="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
var lowCaseChars="abcdefghijklmnopqrstuvwxyz";

for( var i=0; i < 4; i++ )
{  
    text += numChars.charAt(Math.floor(Math.random() * numChars.length));
    text += upCaseChars.charAt(Math.floor(Math.random() * upCaseChars.length));
    text += lowCaseChars.charAt(Math.floor(Math.random() * lowCaseChars.length));
}
console.log(text);

我认为它应该可以解决问题，你可以测试它here。

Answer 3

遵循同样的理念，你可以尝试这样的事情。您将生成一个随机字符串，每个字符串至少包含4个字符（因此至少12个字符），最多为您指定为参数的字符数。

var LOWER_CASE_MASK = 'abcdefghijklmnopqrstuvwxyz';
var UPPER_CASE_MASK = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ';
var NUMBER_MASK = '0123456789';
var ALL_MASK = LOWER_CASE_MASK + UPPER_CASE_MASK + NUMBER_MASK;

function randomString(length) {
  var result = '';
  for (var i = 0; i < 4; i++) {
    result += randomise(LOWER_CASE_MASK);
    result += randomise(UPPER_CASE_MASK);
    result += randomise(NUMBER_MASK);
  }
  for (var j = 0; j < length - 12; j++) {
    result += ALL_MASK[Math.round(Math.random() * (ALL_MASK.length - 1))];
  }
  return shuffle(result);
}

function randomise(string) {
  return string[Math.round(Math.random() * (string.length - 1))];
}

function shuffle(string) {
  var parts = string.split('');
  for (var i = parts.length; i > 0;) {
    var random = parseInt(Math.random() * i);
    var temp = parts[--i];
    parts[i] = parts[random];
    parts[random] = temp;
  }
  return parts.join('');
}

document.write(randomString(20));

shuffle函数是Fisher-Yates shuffle的实现。

Plunker here。

希望这有帮助。

Javascript RegExp生成包含4个小写字母，4个大写字母和1个字符串的字符串。 4个数字

3 个答案: