javascript 数组随机排序 洗牌算法

1、

function shuffle(a) {
  var b = [];

  while (a.length) {
    var index = ~~(Math.random() * a.length);
    b.push(a[index]);
    a.splice(index, 1);
  }

  return b;
}

2、

function shuffle(a) {
  var length = a.length;
  var shuffled = Array(length);

  for (var index = 0, rand; index < length; index++) {
    var random = Math.random() * (index + 1);
    rand = ~~(random);
    rand_ = Math.floor(random);
    console.log(random);
    console.log(rand);
    console.log(rand_);
//     if (rand !== index) 
      shuffled[index] = shuffled[rand];
    shuffled[rand] = a[index];
  }

  return shuffled;
}

3、

function shuffle(array) {
  var _array = array.concat();

  for (var i = _array.length; i--; ) {
    var random = Math.random();
    var j = Math.floor(random * (i + 1));
    
    console.log("i："+i);
    console.log("j："+j);
    console.log("random："+random);
    console.log("==================================");
    
    var temp = _array[i];
    _array[i] = _array[j];
    _array[j] = temp;
  }

  return _array;
}