数组去重、字符串去重....

// 数组去重
var arr = [0, 0, 1, 1, 1, 2, 2, 2, 3, 3, 3, 'a', 'a']
Array.prototype.unique = function () {
  let temp = {},
    newArr = []
  for (let i = 0; i < this.length; i++) {
    if (!temp.hasOwnProperty(this[i])) {
      temp[this[i]] = this[i]
      newArr.push(this[i])
    }
  }
  return newArr
}
console.log(arr.unique()) // [0, 1, 2, 3, "a"]

// --------------------- 分隔线---------------------------

  // 字符串去重
let str = '111222000aabb'
String.prototype.unique = function () {
  let temp = {},
    newStr = ''
  for (let i = 0; i < this.length; i++) {
    if (!temp.hasOwnProperty(this[i])) {
      temp[this[i]] = this[i]
      newStr += this[i]
    }
  }
  return newStr
}
console.log(str.unique()) //'120ab'

// --------------------- 分隔线---------------------------

  // 找出第一个出现次数为1次的字母
let str = 'tyuiatyuibtyuic'
function test(str) {
  var temp = {}
  for (var i = 0; i < str.length; i++) {
    if (temp.hasOwnProperty(str[i])) {
      temp[str[i]]++
    } else {
      temp[str[i]] = 1
    }
  }
  for (var key in temp) {
    if (temp[key] === 1) {
      return key
    }
  }
}
console.log(test(str)); // 'a'