js筛选数组中相同的元素组成新数组

js筛选数组中相同的元素组成新数组

代码

var college = [
	{num:2,lastName:'李世民'},
	{num:1,lastName:'朱元璋'},
	{num:3,lastName:'铁木真'},
	{num:3,lastName:'刘邦'},
	{num:1,lastName:'孙悟空'},
	{num:1,lastName:'刘彻'},
	{num:2,lastName:'曹操'},
	{num:2,lastName:'安吉拉'},
	{num:1,lastName:'赵云'}
];

//先用map结构记录
function arrayToMap(data) {
  //非数组或数据长度为0不处理
  if(!data instanceof Array || data.length == 0) {
    return {};
  }
  var map = {};
  for(var i=0;i<data.length;i++) {
    if(!data[i] instanceof Array || data.length < 2) {
      continue;
    }

    let name = data[i].num;
    if(name != undefined) {
      if(map[name] == undefined) {
        map[name] = [];
      }
      map[name].push(data[i]);
    }
  }
  return map;
}

//把map转成数组
function mapToArray(data) {
  if(data == undefined) {
    return [];
  }
  let array = [];
  for(let p in data) {
    array.push(data[p]);
  }
  return array;
}

//测试
var map = arrayToMap(college);
var array = mapToArray(map);
console.log('筛选后对象',map)
console.log('筛选后数组',array)
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打印效果