js常用本地对象Array使用

Array对象的常用方法：

连接两个或多个数组：concat(array1,array2,…arrayn)

var arr1 = [1,2,3];var arr2 = [4,5,6];console.log(arr1.concat(arr2));//结果是1，2，3，4，5，6console.log(arr2.concat(arr1));//结果是4，5，6，1，2，3var arr3 = [7,8,9];console.log(arr1.concat(arr2,arr3));//结果是1，2，3，4，5，6，7，8，9

concat()的连接顺序是从左往右连接的。

把数组中的所有元素放入一个字符串：join()

var arr = ['A','B','C'];console.log(arr.join());//结果是A,B,Cconsole.log(arr.join("."));//结果是A.B.C

数组元素的添加操作，返回新数组长度：push(),unshift()

var arr1 = ["A","B","C"];var arr2 = ["A","B","C"];console.log(arr1.push("D"));//结果是4console.log(arr1);//结果是["A","B","C","D"]console.log(arr2.push("D","E"));//结果是5console.log(arr2);//结果是["A","B","C","D","E"]var arr3 = ["A","B","C"];var arr4 = ["A","B","C"];console.log(arr3.unshift("D"));//结果是4console.log(arr3);//结果是["D","A","B","C"]console.log(arr4.unshift("D","E"));//结果是5console.log(arr4);//结果是["D","E","A","B","C"]

push()是在数组结尾添加新元素，unshift()是在数组开始处添加新元素。

数组元素的删除操作，返回删除的元素：pop(),shift()

var arr1 = ["A","B","C","D","E"];var arr2 = [];console.log(arr1.pop());//结果是Econsole.log(arr1);//结果是["A","B","C","D"]console.log(arr2.shift());//结果是undefinedvar arr3 = ["A","B","C","D","E"];var arr4 = [];console.log(arr3.shift());//结果是Aconsole.log(arr3);//结果是[,"B","C","D","E"]console.log(arr4.shift());//结果是undefined

pop()是删除数组结尾的元素，shift()是删除数组开始处的元素，并返回删除的值。

选取数组中指定范围的元素：slice(start,end)

var arr1 = ["A","B","C","D","E"]; console.log(arr1.slice(1,3));//结果是["B","C"]console.log(arr1.slice(-3,-1));//结果是["C","D"]

它不会修改原来的数组，返回的是新建的子数组，end是不包括的选取的范围内的，负值传入参数表示从后面开始选取。

向数组中某个位置添加元素或者删除元素，会改变原来的数组结构：splice(index,del,Item…)

var arr1 = ["A","B","C","D","E"];console.log(arr1.splice(2,0,"F"));//返回空数组[]console.log(arr1);//结果是["A","B","C","F","D","E"]var arr2 = ["A","B","C","D","E"];console.log(arr2.splice(2,1,"F","G"));//返回Cconsole.log(arr2);//结果是["A","B","F","G","D","E"]

将数组转换成字符串，并返回结果：toString()

var arr1 = ["A","B","C","D","E"];console.log(arr1.toString());//结果是A,B,C,D,E 

对数组进行排序操作：sort()

var arr1 = [1,5,6,18,3,4,28,2];console.log(arr1.sort(function(a,b){    return a-b;//升序}));//结果是[1, 2, 3, 4, 5, 6, 18, 28]console.log(arr1);//结果[1, 2, 3, 4, 5, 6, 18, 28]

sort()传入的参数必须是函数，默认不写是根据字母顺序来排序，会改变原数组的元素结构。可以通过使用reverse()将数组元素顺序颠倒。