var a = [1, 2, 3, '2', 3, 4, 5, 6, 6, 7, 8, 9, '0', 'a', 'a', 'b'];

// set直接去重
//var set = new Set(a)
//console.log(set)

Array.prototype.unique = function() {
  var newarr = [];
  var flag = true;
  for (var i = 0; i < this.length; i++) {
    for (var j = 0; j < newarr.length; j++) {
      if (newarr[j] === this[i]) {
        flag = false;
        break;
      } else {
        flag = true;
      }
    }
    if (flag) {
      newarr.push(this[i])
    }
  }
  return newarr;
}

Array.prototype.unique2 = function() {
  var newarr = [];
  var flag = true;
  var i = this.length;
  var j = 0;
  while ( --i > 0) {
    j = newarr.length;
    while (--j >= 0) {
      flag = newarr[j] !== this[i];
      if (!flag) {break}
    }
  flag && newarr.push(this[i])
  }
  return newarr.reverse();  //reverse 修改原始数组
}

// 对象去重法  数字和字符串数字无法去重
Array.prototype.unique3 = function() {
  var obj = {}, newarr = [];
  for (var i = 0, length = this.length; i < length; i++ ) {
    //console.log(typeof this[i])
    obj[this[i]] = ""
  }
  console.log(obj)
}

Array.prototype.unique4= function() {
  var obj = {}, newarr = [];
  for (var i = this.length - 1; i >= 0; i -- ) {
    if (obj[this[i]] == undefined) {  //如果取的值在里面是undefined 即代表里面没有该数据
      obj[this[i]] = "";
      newarr.push(this[i]);
    }
  }
  return newarr;
}

// 保证数据类型的保留
Array.prototype.unique5= function() {
  var obj = {}, newarr = [];
  for (var i = this.length - 1; i >= 0; i -- ) {
    if (obj[this[i]] == undefined || obj[this[i]] !== this[i]) { // 将字符串和非字符串区分
      obj[this[i]] = this[i];
      newarr.push(this[i]);
    }
  }
  return newarr.reverse();
}

Array.prototype.unique7 = function() {
  var obj = {}, newarr = [], i = this.length;
  while ( -- i >= 0) {
     (obj[this[i]] == undefined || obj[this[i]] !== this[i]) && (obj[this[i]] = this[i], newarr.push(this[i]))
  }
  return newarr.reverse();
}

//正则表达式法   不考虑字符串和数字类型的判断
Array.prototype.unique8 = function() {
  return this.join(",").match(/([^,]+)(?!.*\1)/ig);
}

console.log(a.unique8())