数组去重方法

双重循环

1.

Array.prototype.unique = function () {
  const newArray = [];
  let isRepeat;
  for (let i = 0; i < this.length; i++) {
    isRepeat = false;
    for (let j = 0; j < newArray.length; j++) {
      if (this[i] === newArray[j]) {
        isRepeat = true;
        break;
      }
    }
    if (!isRepeat) {
      newArray.push(this[i]);
    }
  }
  return newArray;
}

2.

Array.prototype.unique = function () {
  const newArray = [];
  let isRepeat;
  for (let i = 0; i < this.length; i++) {
    isRepeat = false;
    for (let j = i + 1; j < this.length; j++) {
      if (this[i] === this[j]) {
        isRepeat = true;
        break;
      }
    }
    if (!isRepeat) {
      newArray.push(this[i]);
    }
  }
  return newArray;
}

3.

Array.prototype.unique = function () {
  const newArray = [];

  for (let i = 0; i < this.length; i++) {
    for (let j = i + 1; j < this.length; j++) {
      if (this[i] === this[j]) {
        j = ++i;
      }
    }
    newArray.push(this[i]);
  }
  return newArray;
}

Array.prototype.indexOf()

1.

Array.prototype.unique = function () {
  return this.filter((item, index) => {
    return this.indexOf(item) === index;
  })
}

2.

let arr = [1, 2, 3, 22, 233, 22, 2, 233, 'a', 3, 'b', 'a'];
Array.prototype.unique = function () {
  const newArray = [];
  this.forEach(item => {
    if (newArray.indexOf(item) === -1) {
      newArray.push(item);
    }
  });
  return newArray;
}

Array.prototype.sort()

1.

Array.prototype.unique = function () {
  const newArray = [];
  this.sort();
  for (let i = 0; i < this.length; i++) {
    if (this[i] !== this[i + 1]) {
      newArray.push(this[i]);
    }
  }
  return newArray;
}

2.

Array.prototype.unique = function () {
  const newArray = [];
  this.sort();
  for (let i = 0; i < this.length; i++) {
    if (this[i] !== newArray[newArray.length - 1]) {
      newArray.push(this[i]);
    }
  }
  return newArray;
}

###　 Array.prototype.includes()

Array.prototype.unique = function () {
  const newArray = [];
  this.forEach(item => {
    if (!newArray.includes(item)) {
      newArray.push(item);
    }
  });
  return newArray;
}

Array.prototype.reduce()

Array.prototype.unique = function () {
  return this.sort().reduce((init, current) => {
    if(init.length === 0 || init[init.length - 1] !== current){
      init.push(current);
    }
    return init;
  }, []);
}

对象键值对

1.

Array.prototype.unique = function () {
  const newArray = [];
  const tmp = {};
  for (let i = 0; i < this.length; i++) {
    if (!tmp[typeof this[i] + this[i]]) {
      tmp[typeof this[i] + this[i]] = 1;
      newArray.push(this[i]);
    }
  }
  return newArray;
}

2.

Array.prototype.unique = function () {
  const newArray = [];
  const tmp = {};
  for (let i = 0; i < this.length; i++) {
    // 使用JSON.stringify()进行序列化
    if (!tmp[typeof this[i] + JSON.stringify(this[i])]) {
      // 将对象序列化之后作为key来使用
      tmp[typeof this[i] + JSON.stringify(this[i])] = 1;
      newArray.push(this[i]);
    }
  }
  return newArray;
}

Map

1.

Array.prototype.unique = function () {
  const newArray = [];
  const tmp = new Map();
  for(let i = 0; i < this.length; i++){
        if(!tmp.get(this[i])){
            tmp.set(this[i], 1);
            newArray.push(this[i]);
        }
    }
    return newArray;
}

2.

Array.prototype.unique = function () {
  const tmp = new Map();
  return this.filter(item => {
    return !tmp.has(item) && tmp.set(item, 1);
  })
}

Set

Array.prototype.unique = function () {
  const set = new Set(this);
  return Array.from(set);
}

Array.prototype.unique = function () {
  return [...new Set(this)];
}

原生 js 实例封装

Array.prototype.myUnique = function () {
            var obj = {};
            for(var i = 0; i < this.length; i++) {
                var cur = this[i];
                if(obj[cur] === cur){
                    this[i] = this[this.length-1];
                    this.length--;
                    i--;
                    continue;
                }
                obj[cur] = cur;
            }
                obj = null;
                return this;
         }