6. Object.hasOwn() 特性: ES2022 引入的安全检查方法 替代hasOwnProperty () 避免原型链和 this 绑定问题 javascript // 安全检查示例functionhasProp(obj,key){returnObject.hasOwn(obj,key);} 对比测试: javascript // 性能对比(100万次检查)Object.hasOwn:18ms obj.hasOwnProperty:22ms 四、进阶遍历技巧 ...
Object.getOwnPropertyNames(["a","b"])//[ "0", "1", "length" ] Object.keys(["a","b"])//[ "0", "1" ] Object.getPrototypeOf([]);//Array [] constobj={name:"sam",sex:"male",say:function(){}}; obj.hasOwnProperty("name");//true obj.propertyIsEnumerable("name");//true ...
一、Array.prototype.{flat, flatMap} 扁平化嵌套数组 1.1 Array.prototype.flat 1.1.1 定义 1.1.2 语法 1.1.3 返回值 1.1.4 举例 1.1.5 注意 1.1.6 替换 1.2 Array.prototype.flatMap 1.2.1 定义 1.2.2 返回值 1.2.3 语法 1.2.4 举例 二、Object.fromEntries 2.1 定义 2.2 返回值 2.3 语法 2.4 举...
consthome="c:\\temp"; 也可以在换行之前加上反斜杠以转义换行。这样反斜杠和换行都不会出现在字符串的值中。 js conststr="this string \ is broken \ across multiple \ lines.";console.log(str);// this string is broken across multiple lines....
使用字面量创建的对象也会有一个指向该对象构造函数类型的 constructor 属性,例如,数组字面量创建的 Array 对象和对象字面量创建的普通对象。jsCopy to Clipboard const o1 = {}; o1.constructor === Object; // true const o2 = new Object(); o2.constructor === Object; // true const a1 = [];...
在JavaScript中,Object.freeze()工具函数可以冻结一个对象。让我们来冻结Sizes枚举: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 constSizes=Object.freeze({Small:'small',Medium:'medium',Large:'large',})constmySize=Sizes.Medium console.log(mySize===Sizes.Medium)// logs true ...
In the callback function, we are passing the value of this object with the first property set to 4. Hence checking whether the task. The id is equal to this[0] or not will return an object with id 4. Conclusion In this post, we learned about the JavaScript Array find me...
We can also add a property to an object in an array of objects using themapmethod in JavaScript. Themap()method creates a new array by calling a function on each element in the given array. constpersonArr = [{name:'John'}, {name:'Tom'}, {name:'David'}]constnewArr = personArr....
Length of an Array. We can find the length of an array using the length property. For example, const dailyActivities = [ "eat", "sleep"]; // return the length of array console.log(dailyActivities.length); // Output: 2 Run Code Relationship between arrays and objects in JavaScript....
prototypeis a property available with all JavaScript objects. Syntax Array.prototype.name=value Warning You are not advised to change the prototype of an object that you do not control. You should not change the prototype of built in JavaScript datatypes like: ...