数组降维-去重-排序

let arr = [1,23,[121,1,53,[234,342,324,[234,432],234]]]

快速实现

let arr1 = arr.flat(Infinity) //降维
  let arr2 = Array.from( new Set(arr1)) //去重，转为数组
  let arr3 = arr2.sort((a,b)=>(a-b)) // 排序
  console.log(arr3)

数组降维方法

1：递归

var arr1 = [[0, 1], [2, 3], [4, 5]];
var arrFn=(arr)=> ( [].concat( ...arr.map(x => Array.isArray(x) ? arrFn(x) : x) ) )
arrFn(arr1)



  var arr = [[1, 2, 3], 4, 5, 6, [[7]], []] //多维数组
	const res = []
	function fn(array) {
	  for (var i of array) {
	    if (Array.isArray(i)) {
	      fn(i)
	    } else {
	      res.push(i)
	    }
	  }
	}
	fn(arr)
  console.log(res

2：Array.flat()

const newArr = arr.flat() //参数为展开嵌套深度（number类型）

参数： 
	Infinity 展开任意深度的嵌套数组

数组去重

1：filter方法

function fn(arr) {
  let newArr = arr.filter((item, index) => {
    return arr.indexOf(item, 0) === index
  })
  return newArr
}
console.log(fn(arr))

2：set方法

let arr = [1,22,1,3,[2,1,32,[1,3,43,24,23532,4,32],1,3]]
  
  let newArr = Array.from( new Set(arr)) //去重，转为数组
  let newArr = [...new Set(arr)] //去重，转为数组

数组排序

1：sort

let arr = [1, 4, 6, 7, 3, 5, 8];
  
  let arr1 = arr.sort((a,b)=>(a-b)) //a-b 升序  b-a 降序

2：冒泡排序

let arr = [1, 4, 6, 7, 3, 5, 8];
  let max = 0;
  for (let i = 0; i < arr.length; i++) {
      for (let j = 0; j < arr.length - i - 1; j++) {
          if (arr[j] > arr[j + 1]) {  // > 升序  < 降序
              max = arr[j];
              arr[j] = arr[j + 1];
              arr[j + 1] = max;
          }
      }
  }
  console.log(arr);

3：选择排序

let arr = [1, 4, 6, 7, 3, 5, 8];
  var temp;
  for(var i=0;i<arr.length-1;i++){
      for(var j=i+1;j<arr.length;j++){
          if(arr[i]>arr[j]){
              temp=arr[i];
              arr[i]=arr[j];
              arr[j]=temp;
          }
      }
  }
  console.log(arr)

4：希尔排序

function xier(arr){
    var interval = parseInt(arr.length / 2);  //分组间隔设置
    while(interval > 0){
        for(var i = 0 ; i < arr.length ; i ++){
            var n = i;
            while(arr[n] < arr[n - interval] && n > 0){
                var temp = arr[n];
                arr[n] = arr[n - interval];
                arr[n - interval] = temp;
                n = n - interval;
            }
        }
        interval = parseInt(interval / 2);
    }
    return arr;
}

console.log(xier([12,9,38,44,7,98,35,59,49,88,38]))

补充 对象数组排序

//对象数组排序
var arr = [
    {name:'syy',age:0},
    {name:'wxy',age:18},
    {name:'slj',age:8},
    {name:'wj',age:20}
];
 
function compare(property){
    return function(a,b){
        var value1 = a[property];
        var value2 = b[property];
        return value1 - value2;//升序,降序为value2 - value1
    }
}
arr.sort(compare('age'))
console.log(arr)