JavaScript Array对象知识点总结

Array对象用于在变量中存储多个值。

• length: 返回数组元素的个数

let arr01 = ["America", "Banana", "Coke Cola"];
document.write("arr01.length: " + arr01.length); // 3
arr01.length = 10;
document.write("arr01.length: " + arr01.length); // 10

• concat(): 连接多个数组并返回结果

let arr01 = ["America", "Banana", "Coke Cola"];
let arr02 = ["Wonderful", "Deeppink", "Electronic"];
let resArr = arr01.concat(arr02);
document.write("<br/>resArr: " + resArr); // resArr: America,Banana,Coke Cola,Wonderful,Deeppink,Electronic
document.write("<br/>resArr's length: " + resArr.length); // resArr's length: 6
 
// 合并多个数组
var firstNameArr = ["name01", "name02"];
var secNameArr = ["name03", "name04"];
var thirdNameArr = ["name05", "name06"];
var lastNameArr = ["name07", "name08"];
var resNameArr = firstNameArr.concat(secNameArr, thirdNameArr, lastNameArr);
// name01,name02,name03,name04,name05,name06,name07,name08
document.write("resNumberArr: " + resNameArr);

• every(): 数组元素条件检查：只有所有的元素满足条件才会返回true

function checkAgeRange(age) {
  return age >= 0 && age <= 100;
}  
let arrAge = [18, 15, 17, 19, 20];
let res01 = arrAge.every((x) => {x >= 18}); // false
let res02 = arrAge.every(checkAgeRange); // true

• join(): 将数组元素组装成一个字符串

var nameList = ["wangzz", "wangyt", "loveforever"];
document.write(nameList.join()); // wangzz,wangyt,loveforever

• pop(): 删除数组最后一个元素

var nameList = ["wangzz", "wangyt", "loveforever"];
document.write(nameList.pop()); // loveforever
document.write("<br/>nameList after pop: " + nameList); // nameList after pop: wangzz,wangyt

• push(): 向数组中添加新元素

var nameList = ["wangzz", "wangyt", "loveforever"];
nameList.push("Felix");
document.write(nameList); // wangzz,wangyt,loveforever,Felix

• reverse(): 数组翻转

var nameList = ["wangzz", "wangyt", "loveforever"];
document.write(nameList.reverse());

• shift(): 删除数组中第一个元素

var nameList = ["wangzz", "wangyt", "loveforever"];
document.write(nameList.shift()); // wangzz
document.write("<br/> nameList after shift :" + nameList); // nameList after shift :wangyt,loveforever

• splice()&slice() 截取指定范围内的数组元素

var nameList = ["wangzz", "wangyt", "loveforever"];
document.write(nameList.slice(1,2)); // wangyt
document.write("<br/>" + nameList.splice(1,1)); // wangyt

• sort(function(a,b){return a - b;}: 升序 | sort(function(a,b){return b - a;}: 降序

// 数组按降序进行排序
var points = [40, 100, 1, 5, 25, 10];
points.sort(function(a, b) {return b - a});
document.write(points); // 100,40,25,10,5,1
// 数组按升序进行排序
points.sort(function(a, b) {return a - b});
document.write("<br/>" + points); // 1,5,10,25,40,100

• splice()在指定的索引位置添加元素

var points = [40, 100, 1, 5, 25, 10];
points.splice(2, 0, "9999", "99999");
document.write(points); // 40,100,9999,99999,1,5,25,10

• toString() 将数组转为字符串

var fruits = ["nameA", "nameB", "nameC"];
document.write(fruits.toString()); // nameA,nameB,nameC

• unshift: 从开头添加一个元素

var fruits = ["nameA", "nameB"];
document.write(fruits.unshift("nameC")); // 3
document.write("<br/>" + fruits); // nameC,nameA,nameB