JavaScript ------（一）Array 对象

Array对象方法

创建数组

let fruits = ["apple", "panapple"];

通过索引访问数组元素

let fruits = ["apple", "panapple"];

let first = fruits[0];
let second = fruits[1];

console.log(first);
//apple
console.log(second);
//panapple

遍历数组

let fruits = ["apple", "panapple"];

fruits.foreach(function(item,index){
    console.log("index["+index+"]---"+item);
    //index[0]---apple
    //index[1]---panapple
});

添加元素到数组的末尾

let fruits = ["apple", "panapple"];

let newFruits = fruits.push("banana");
//newFruits---["apple", "panapple", "banana"];

删除数组末尾的元素

let fruits = ["apple", "panapple"];

let newFruits = fruits.push("banana");

let delLast = newFruits.pop() 
//delLast---["apple", "panapple"];

找出某个元素在数组中的索引

let fruits = ["apple", "panapple"];

let pos = fruits.indexof("apple"); 
//0

根据索引删除或者增加数组中某个元素：splice(index,num,item)　　index--必选，添加\删除元素的位置；num--必选，删除项目数量，0为不删除；item--可选，添加的元素，可为多个

let fruits = ["apple", "panapple"];

let newfruits = fruits.splice(0,1); 

//delLast---["panapple"]

let newfruits = fruits.splice(0,0,"orange"); 
//delLast---["orange","apple", "panapple"]

截取数组中的部分

let fruits = ["apple", "panapple", "orange"];
let newfruits = fruits.slice(); 
//newfruits ---["apple", "panapple"，"orange"]
let newfruits = fruits.slice(1,2);
//newfruits ---["panapple"，"orange"]

 连接两个或者更多的数组

let fruit = ["apple","pine","orange","banana"];
let tool = ["pen","pencile","rule","map"];
console.log(fruit.concat(tool));
//(8) ["apple", "pine", "orange", "banana", "pen", "pencile", "rule", "map"]
console.log(fruit.concat("pen","pencile","rule","map"));
//(8) ["apple", "pine", "orange", "banana", "pen", "pencile", "rule", "map"]

对数组进行排序

let fruit = ["apple","pine","orange","banana"];
console.log(fruit.sort());
//(4) ["apple", "banana", "orange", "pine"]
let number = [7,3,7,6,5,1,2];
console.log(number.sort());
//(7) [1, 2, 3, 5, 6, 7, 7]
//如果是两位数，只会根据最高位数字大小排序，故如需要排序，可以在sort(function(){})里面定义排序方法

将数组转换成字符串

let fruit = ["apple","pine","orange","banana"];
console.log(fruit.toString());
//apple,pine,orange,banana

将数组转换成本地字符串（在处理数据可巧用，非常nice）

let fruit = ["apple","pine","orange","banana"];
console.log(fruit.toLocaleString());
//apple,pine,orange,banana

let number = 2333333;
console.log(number.toLocaleString());
//2,333,333
console.log(number.toLocaleString("zh",{style:"decimal"}));
//2,333,333
console.log(number.toLocaleString("zh",{style:"percent"}));
//233,333,300%
console.log(number.toLocaleString("zh",{style:"currency"}));
//报错
console.log(number.toLocaleString("zh",{style:"currency",currency:"CNY"}));
//¥2,333,333.00
console.log(number.toLocaleString("zh",{style:"currency",currency:"cny",currencyDisplay:"code"}));
//CNY 2,333,333.00
console.log(number.toLocaleString("zh",{style:"currency",currency:"cny",currencyDisplay:"name"}));
//2,333,333.00人民币

 

Array对象属性

获取数组长度

let fruit = ["apple","pine","orange","banana"];
console.log("fruit.length-----"+fruit.length);
//fruit.length-----4