数组常用api

数组常用api

字面量

let arr = [1, 2, "a", "b", true, false, { x: 1, y: 2 }, [1, 2], function () {}];
      console.log(arr);

…rest

arr = [4, 5, 6];
      let arr1 = [...arr];
      console.log(arr1);

Array.of

let a = [1, 2, 3, 4, 5, 6, true, function () {}];
      arr = Array.of(...a);
      console.log(arr);

Array.from

const likeArr = {
        0: "家",
        1: "公司",
        2: "学校",
        length: 3,
      };
      console.log(likeArr);
      console.log(Array.from(likeArr));

尾部增删，push从左到右进入，pop从右到左删除

let arr = [];
console.log(arr.push(1));
      console.log(arr.push(2, 3));
      console.log(arr);
      console.log(arr.pop());
      console.log(arr.pop());
      console.log(arr.pop());

头部增删，unshift从右到左增加，shift从左到右删除

 console.log(arr.unshift(1));
      console.log(arr.unshift(3, 2));
      console.log(arr);
      console.log(arr.shift());
      console.log(arr.shift());
      console.log(arr.shift());
      console.log(arr);

delete：删除指定的

 arr = [1, 2, 3, 4, 5, 6, 7];
      delete arr[4];
      console.log(arr);
      arr.length = 4;
      console.log(arr);

forEach((item,index,arr)=>{…})每个元素逐个调用，没有返回值

let arr = [4, 5, 6, 7];
      arr.forEach((item, index, arr) => console.log(item, index, arr));

map；参数与功能与forEach一样，只是有返回值

res = arr.map(item => item * 2);
      console.log(res);

every,some 断言函数，返回true,false
every:数组成员全部满足条件，返回true,否则false

console.log(arr.every(item => item >= 0));
      console.log(arr.every(item => item >= 5));

some:数组成员有一个满足条件，返回true，否则false

console.log(arr.some(item => item >= 6));
      console.log(arr.some(item => item >= 8));

filter:返回数组满足条件的元素，组成新数组,find返回新数组的第一个元素，findIndex返回新数组的第一个索引

console.log(arr.filter(item => item >= 5));
      console.log(arr.find(item => item >= 6));
      console.log(arr.findIndex(item => item >= 6));

reduce 归并

 res = arr.reduce(function (acc, cur, index, arr) {
        return acc + cur;
      }, 5);
      console.log(res);

sort 排序

let arr = [20, 30, 14, 53];
      console.log(arr.sort());
      console.log(arr.sort((a, b) => a - b));//升序
      console.log(arr.sort((a, b) => b - a));//降序

join:array->String

arr = ["a", "b", "c"];
      console.log(arr.join());
      console.log(arr.join("-"));

splice:删除，新增，替换

console.log(arr);
      console.log(arr.slice(5, 2));
      console.log(arr);
      console.log(arr.splice(1, 2, "a", "b"));
      console.log(arr);
      console.log(arr.slice(2, 0, "red", "green"));
      console.log(arr);
      let data = ["red", "green", "blue"];
      console.log(arr.splice(2, 0, ...data));
      console.log(arr);