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常用的数组方法

常用的数组方法

作者: 詹小云 | 来源:发表于2016-12-13 19:56 被阅读0次

    数组的方法有许多,但来来回回常用的也就那几种,特此记录,以备遗忘之需。

    将数组合并成字符串

    1. toString()
      直接把数组里的内容变成一个字符串
      var arr = [12,25,30,92]; var arr1 = arr.toString(); //arr1 = 12,25,30,92
    2. join()
      以某种符号将数组内容串联成一个字符串
      var arr = [12,25,30,92]; var arr1 = arr.join('*'); //arr1 = 12*25*30*92

    增加数组内容

    1.push()
    添加的内容按顺序放在数组最后面,并自动加长度

    var arr = [12,25,30,92];
    var arr1 = arr.push(51,65); //arr1 = [12,25,30,92,51,65]
    

    2.unshift()
    添加的内容按顺序放在数组的最前面,并自动增加长度

    var arr = [12,25,30,92];
    var arr1 = arr.unshift(51,65); //arr1 = [51,65,12,25,30,92]
    

    取出数组内容

    1.pop()
    取出数组最后一个元素,并返回该值且在数组中消失

    var arr = [12,25,30,92];
    var poped = arr.pop();
     //arr = [12,25,30]   poped = 92
    

    2.shift()
    取出数组第一个元素,并返回该值且在数组中消失

    var arr = [12,25,30,92];
    var shifted = arr.shift();
     //arr = [25,30,92]   shifted = 12
    

    3.slice(begin,end)
    浅复制了数组内容,begin为开始复制的位置,end为结束复制的位置

    var arr = [12,25,30,92];
    var arr1 = arr.slice(1,3);
     //arr1 = [25,30,92]  
    

    排序

    排序的方法倒是只有一种,即sort(),但是分为升序和降序
    1.升序
    默认为升序

    var arr = [12,0,25,30,92];
    var arr1 = arr.sort();
    //arr1 = [0,12,25,30,92]
    

    还有另一种写法记得ab不能写反

    var arr = [12,0,25,30,92];
    var arr1 = arr.sort(functiion(a,b){
          return a-b;
    });
    //arr1 = [0,12,25,30,92]
    

    2.降序

    var arr = [12,0,25,30,92];
    var arr1 = arr.sort(functiion(a,b){
          return b-a;
    });
    //arr1 = [92,30,25,12,0]
    

    替换数组内容

    splice(start,items,inplace);此方法从数组的start位置开始删除items个元素,并添加inplace元素

    var myFish = ['angel', 'clown', 'mandarin', 'surgeon'];
    // removes 0 elements from index 2, and inserts 'drum'
    var removed = myFish.splice(2, 0, 'drum');
        // myFish is ['angel', 'clown', 'drum', 'mandarin', 'surgeon']
        // removed is [], no elements removed
    // myFish is ['angel', 'clown', 'drum', 'mandarin', 'surgeon']
     // removes 1 element from index 3
    removed = myFish.splice(3, 1);
        // myFish is ['angel', 'clown', 'drum', 'surgeon']
        // removed is ['mandarin']
    // removes 1 element from index 2, and inserts 'trumpet'
    removed = myFish.splice(2, 1, 'trumpet');
        // myFish is ['angel', 'clown', 'trumpet', 'surgeon']
        // removed is ['drum']
     // removes 2 elements from index 0, and inserts 'parrot', 'anemone' and 'blue'
    removed = myFish.splice(0, 2, 'parrot', 'anemone', 'blue');
        // myFish is ['parrot', 'anemone', 'blue', 'trumpet', 'surgeon']
        // removed is ['angel', 'clown']
     // removes 2 elements from index 2
    removed = myFish.splice(myFish.length -3, 2);
        // myFish is ['parrot', 'anemone', 'surgeon']
        // removed is ['blue', 'trumpet']
    

    这一个引用了devdocs的demo

    合并数组

    concat();将两个数组合并成一个新数组,并返回该数组

    var arr1 = [12,23,34];
    var arr2 = ['hello','world'];
    var arr3 =arr1.concat(arr2);
    //arr3 = [12,23,34,'hello','world']
    

    哪个数组使用了此方法,哪个就在前

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