var arr=[1,10,5,7,15];
alert(arr.reverse());//15,7,5,10,1
alert(arr);//15,7,5,10,1 reverse方法会改变原来的数组

var arr=[1,10,5,7,15];
alert(arr.sort)//1,10,15,5,7;
//如果没有指定函数，则按unicode编码排序
function sortNum(a,b){
console.log("a"+a);
console.log("b"+b);
return a-b; //按从小到大的顺序排列;b-a则相反
}
alert(arr.sort(sortNum));//1,5,7,10,15
alert(arr);//1,5,7,10,15改变了原数组

 
var colors=["red","green","blue"];
var colors2=colors.concat("yellow",["black","brown"]);
alert(colors);//red,green,blue;原数组不变
alert(colors2)//red,green,blue,yellow,black,brown

var colors=["red","green","blue","black"];
alert(colors.slice(1));//green,blue,black;
alert(colors.slice(1,3));//green,blue//不包括结束项
alert(colors.slice(3,1));//空
alert(colors);//red,green,blue,black//不会影响原数组

var colors=["red","green","blue"];
var removed=colors.splice(0,1);//删除第一项
alert(colors);//green,blue;//会改变原数组
alert(removed)//red
 
removed=colors.splice(1,0,"yellow","orange");//从位置1插入2项
alert(colors);//green,yellow,orange,blue
alert(removed);//空数组，没有删除
 
removed=colors.splice(1,1,"red","purple");//插入2项，删除一项
alert(colors);//green,red,purple,orange,blue
alert(removed);//yellow,返回的数组中只包含一项

var numbers=[1,2,3,4,5,4,3,2,1]
alert(numbers.indexOf(4))//3
alert(numbers.lastIndexOf(4));//5
alert(numbers.indexOf(4,4));//5
alert(numbers.lastIndexOf(4,4));//3
var person={name:"nicholas"};
var people=[{name:"nicholas"}];
var morepeople=[person]
alert(people.indexOf(person));//-1; s
alert(morepeople.indexOf(person));//0;

迭代方法

Array.prototype.every() :

var numbers=[1,2,3,4,5,4,3,2,1];
var everyResult=numbers.every(function(item,index,array){
return (item>2);//检测数组中的每一项是否满足大于2,满足则返回true,否则false;
});
alert(everyResult);//false

Array.prototype.filter():

var filterResult=numbers.filter(function(item,index,array){
return (item>2);//相当于一个过滤器
});
alert(filterResult);//[3,4,5,4,3];

Array.prototype.forEach()：

Array.prototype.map():

var mapResult=numbers.map(function(item,index,array){
return item*2;//返回乘2后的结果
});
alert(mapResult);//[2,4,6,8,10,8,6,4,2]

Array.prototype.some():

var someResult=numbers.some(function(item,index,array){
return (item>2);//检测数组中的任意一项是否满足大于2,满足则返回true,否则false;
});
alert(someResult);//true

归并方法

reduce()和reduceRight()

var values=[1,2,3,4,5];
var sum=values.reduce(function(prev,cur,index,array){
console.log("prev"+prev);
console.log("cur"+cur);
return prev+cur;
});
alert(sum);//15

将二维数组转化为一维

var flattened = [[0, 1], [2, 3], [4, 5]].reduce( function(a, b) {
return a.concat(b);
}, [] ); // flattened is [0, 1, 2, 3, 4, 5]

计算数组中每个元素出现的次数

var names = ['Alice', 'Bob', 'Tiff', 'Bruce', 'Alice'];
var countedNames = names.reduce(function (allNames, name) {
// allNames在这里是一个累加器，将数组中的值一键值对的形式存储
if (name in allNames) {
console.log(allNames);//里面存了对象allNames{Alice:1,Bob,1...}
console.log(name);//Alice,Bob,Tiff,Bruce,Alice
allNames[name]++;
}
else {
allNames[name] = 1;
}
return allNames;
}, {});//第二个参数这个括号不能少，不知道为什么。。。
// console.log(countedNames);
// countedNames is:
// { 'Alice': 2, 'Bob': 1, 'Tiff': 1, 'Bruce': 1 }