1：Array对象用于在单个变量中存储多个值

typeof(arrArr) 'object'

var arr1 = [];//创建一个空数组

eg：数组是个引用类型

var a = [1,2,3];

var b = [1,2,3];

console.log(a == b);

//false

构造函数创建

var arr1 = new Array();//创建空数组

var arr2 = new Array(10)；//创建一个长度为10的数组

new Array(-1); //Uncaught RangeError: Invalid array length(…)

new Array(undefined) //[undefined]

var arr3 = new Array(5,4,3,2,1)；//创建数组并初始化

es6 Array.of 创建数组

Array.of()

//[]

Array.of(undefined)

//[undefined]

Array.of(1)

//[1]

Array.of(3)

//[3]

Array.of(1, 2)

//[1, 2]

Array.of(-1)

//[-1]

2：length 属性

var arrArr = [1,2,3,4,5];

console.log(arrArr.length); //5

数组的最后一项是length-1

console.log(arrArr[arrArr.length-1]) //5

3:数组的遍历

var arrArr = [1,2,3,4,5];

for (var i = 0; i < arrArr.length; i++) {

　　//arrArr[i]....

};

4：数组中常见的方法

(1)删除数组的最后一项，返回的是删除的值

pop()

eg:

var arr = ["1","2"];

var arrv=arr.pop();

console.log(arr);

console.log(arr2);

//["1"]

//2

(2) 向数组的最后添加值,返回的是新数组的长度

push()

eg:

var arr = ["1","2"];

var arrv=arr.push("3","4","5");

console.log(arr);

console.log(arrv);

//["1", "2", "3", "4", "5"]

//5

(3) 删除数组的第一项，返回的是删除的值

shift()

eg:

var arr = ["1","2"];

var arrv=arr.shift();

console.log(arr);

console.log(arrv);

//["2"]

//1

(4) 向数组的开头添加值,返回的是新数组的长度

unshift()

eg:

var arr = ["1","2"];

var arrv=arr.unshift("3","4","5");

console.log(arr);

console.log(arrv);

//["3", "4", "5", "1", "2"]

//5

(5)concat()

合并两个数组,原数组不变。concat是把arr1和arr2合并为一个新数组返回

eg:

var arr1 = ["1","2"];

var arr2 = ["3","4"];

var newarr=arr1.concat(arr2,["5","6"]);

console.log(arr1);

console.log(arr2);

console.log(newarr);

//["1", "2"]

//["3", "4"]

// ["1", "2", "3", "4", "5", "6"]

(6)slice英文意思是：切成片,切下,划分

slice()

arrayObject.slice(start,end)

从已有的数组中返回选定的元素,从下标为start的元素开始,若为负数,表示从最后开始,-1表示最后一项,

到下标为end之前的一项

eg:

var arr1 = ["1","2","3","4","5"];

var arr2 = arr1.slice(1,4);

console.log(arr1);

console.log(arr2);

//["1", "2", "3", "4", "5"]

//["2", "3", "4"]

(7)splice()

从数组中添加删除项,返回被删除的项目。

arrayObject.splice(index,howmany,item1,.....);

index规定的是添加删除项的位置,若为负数,表示从最后开始,-1表示最后一项

howmany表示的是要删除的项目的数量。为0表示的是不删除。只是添加

item1,.....向数组中添加的新项(可选)

eg:

var arr = ["A","B","C","D","E","F","G"];

var newarr=arr.splice(2,4,"1");

console.log(arr);

console.log(newarr);

//["A", "B", "1", "G"]

//["C", "D", "E", "F"] 被删除的项

eg:

var arr = ["A","B","C","D","E","F","G"];

var newarr=arr.splice(2,0,"1");

console.log(arr);

console.log(newarr);

//["A", "B", "1", "C", "D", "E", "F", "G"]

//[] 表示的是删除0项

eg:

var arr = ["A","B","C","D","E","F","G"];

var newarr=arr.splice(2,3); //只删除不添加

console.log(arr);

console.log(newarr);

//["A", "B", "F", "G"]

//["C", "D", "E"]

(8)reverse()

颠倒数组中元素的顺序(改变的是原数组)

arrayObject.reverse();

var arr = ["A","B","C","D","E","F","G"];

var arr1=arr.reverse();

console.log(arr);

console.log(arr1);

//["G", "F", "E", "D", "C", "B", "A"]

//["G", "F", "E", "D", "C", "B", "A"]

(9)sort()

对数组的元素进行排序(默认是按照字符集的格式进行排序)

sortby规定排序的顺序,必须是函数

arrayObject.sort(sortby);

var arr = [1,3,2,4,6,9];

arr.sort();

console.log(arr);

//[1, 2, 3, 4, 6, 9]

sortby规定排序的顺序,只能是个函数。两参数的差值小于0，则表示a必须出现在b前面，否则在b后面

若 a 小于 b，在排序后的数组中 a 应该出现在 b 之前，则返回一个小于 0 的值。

若 a 等于 b，则返回 0。

若 a 大于 b，则返回一个大于 0 的值。

var arr = [2,5,4,23,2,45];

arr.sort(function(a,b){

　　if(a < b){

　　　　return -1;  //a-b返回一个小于0.a在b的前面。a比b小。升序排列

　　}else if(a > b){

　　　　return 1;  //a-b返回一个大于0.说明a比b大。升序排列。a在b的后面

　　}else if(a == b){

　　　　return 0; //a-b返回一个等于0.说明a等于b。

　　}

});

console.log(arr);

//[2, 2, 4, 5, 23, 45]

(10)join()

把数组中的所有元素放入一个字符串中

separator为分隔符

arrayObject.join(separator)

eg:

var arr = [1,2,3,4,5,6,7];

var str = arr.join(",");

console.log(str);

//1,2,3,4,5,6,7