js中改变原数组的方法

pop(),push(),shift(),unshift(),sort(),reverse(),splice()

        var s1 = ["s", 1, 4, 9, 0, 1];
        let mm = s1.pop();
        console.log(s1); //["s", 1, 4, 9, 0]  原来的数组发生了改变。方法返回的是被删除掉的元素
        console.log(mm); //1

        var s1 = ["s", 1, 4, 9, 0];
        let mm1 = s1.push("newData", "ooo", "lll");
        console.log(s1); // ["s", 1, 4, 9, 0, "newData", "ooo", "lll"]
        console.log(mm1); // 8 返回的是新数组的长度

      从数组的开头删除一个数据
        var s1 = ["s", 1, 4, 9, 0, "newData", "ooo", "lll"];
        let d1 = s1.shift();
        console.log(s1); // // [1, 4, 9, 0, "newData", "ooo", "lll"]
        console.log(d1); // s   返回的是新删除的数据

      从数组的开头增加一个数据
        var s1 = [1, 4, 9, 0, "newData", "ooo", "lll"];
        let mm2 = s1.unshift("one", "two");
        console.log(s1);
        //  ["one", "two", 1, 4, 9, 0, "newData", "ooo", "lll"]
        console.log(mm2); // 9 返回的是新数组的长度

        不加回调函数：
        var k1 = [12, 23, 14, 56, 0, 6, 8];
        k1.sort();
        console.log(k1);
      [0, 12, 14, 23, 56, 6, 8]

        加回调函数：
        var k1 = [12, 23, 14, 56, 0, 6, 8];
        //   k1.sort((num1, num2) => num1 - num2);
        k1.sort((num1, num2) => num2 - num1); // [56, 23, 14, 12, 8, 6, 0]
        console.log(k1);
         a - b 是从小到大排序
       b - a 是从大到小
      [0, 6, 8, 12, 14, 23, 56]

        var k1 = [0, 6, 8, 12, 14, 23, 56];
        k1.reverse();
        console.log(k1);
        // [56, 23, 14, 12, 8, 6, 0]

      var k1 = [56, 23, 14, 12, 8, 6, 0];
      var mm3 = k1.splice(0, 1, "one", "two");
      console.log(k1);
      //  ["one", "two", 23, 14, 12, 8, 6, 0]
      console.log(mm3); // [56]   返回被删除元素所组成的数组
    //   删除56，替换成 "one", "two"