**常用内置对象介绍** - 例子: ``` var a = [1, 2, 3]; var b = [4, 5, 6]; var c = ["one", "two", "three"]; console.log(a.concat(b, c)); ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591526412700) - reverse() 方法，颠倒数组的顺序。实例： ``` var a = [1, 2, 3, 4]; a.reverse(); console.log(a); ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591526475500) - slice() 方法，从某个已有的数组返回选定的元素。语法为： ``` arrayObject.slice(start, end); ``` - 实例：在控制台中输入以下代码 ``` var a = [1, 2, 3, 4, 5, 6]; a.slice(2, 5); ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591526628232) - splice() 方法，删除或替换当前数组的某些项目。语法为： ``` arrayObject.splice(start, deleteCount, options); ``` - 实例：在控制台中输入以下代码 ``` var a = [1, 2, 3, 4, 5, 6]; a.splice(2, 2, "abc"); a; ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591526867261) - sort() 方法，将数组进行排序。实例： ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200606-1591431375355) - charAt() 方法，获取指定位置处字符。语法为：stringObject.charAt(index); ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527068258) - charCodeAt() 方法，获取指定位置处字符的 Unicode 编码。语法为：stringObject.charCodeAt(index); ``` var str = "Hello world!"; document.write(str.charCodeAt(2)); ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527197906) - 综述： ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527477683) ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527504436) ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527521482) **构建对象** 1. 通过对象字面量来创建 ``` var student = { name: "zhangsan", age: 18, gender: "male", sayHi: function() { console.log("hi,my name is " + this.name); } }; ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591527802725) 2.通过 new Object() 创建对象 ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591528637866) 3.通过工厂函数创建对象 ``` function createStudent(name, age, gender) { var student = new Object(); student.name = name; student.age = age; student.gender = gender; student.sayHi = function() { console.log("hi,my name is " + this.name); }; return student; } var s1 = createStudent("zhangsan", 18, "male"); ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591528073546) 4.自定义构造函数 ``` function Student(name, age, gender) { this.name = name; this.age = age; this.gender = gender; this.sayHi = function() { console.log("hi,my name is " + this.name); }; } var s1 = new Student("zhangsan", 18, "male"); ``` **遍历对象的属性通过 for...in 语句用于遍历数组或者对象的属性，对数组或者对象的属性进行循环操作** ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591528380909) **删除属性** ``` var student = { name: "zhangsan", age: 18, gender: "male" }; student.name; // zhangsan delete student.name; student.name; // undefined ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591528485318) **挑战：内置对象使用案例** 1. 写一个函数，格式化日期对象 ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591529285547) 2.写一个函数去掉数组中的重复元素。比如有一个数组 array = ["x", "c", "a", "b", "c", "b", "c"]。 ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591529383617) 3. 写一个函数判断一个字符串中出现次数最多的字符，并统计这个字符出现的次数。比如有这样一个字符串："daskljahiagnaknscsjdwfanalvnahdpwod"。 ``` ``` ![image.png](https://dn-simplecloud.shiyanlou.com/courses/uid1370626-20200607-1591529511959)

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