1、使用 typeof bar === "object" 判断 bar 是不是一个对象有神马潜在的弊端？如何避免这种弊端？使用 typeof 的弊端是显而易见的（这种弊端同使用 instanceof）：let obj = {};let arr = [];console.log(typeof obj === 'object'); //trueconsole.log(typeof arr === 'object'); //true...
其实答案很简单,直接计算key的数量就可以了。 Object.keys(counterArray).length // Output 3 本文给出的面试题答案只是很多合理答案中的几个,可能会不全面,欢迎大家补充。 由于个人疏忽等原因,本文中难免会存在少量错误,欢迎大家批评指正。面试题参考自: 21 Essential JavaScript Interview Questions | Codementor 编辑...
闲来无事,正好切一下。 一 What is a potential pitfall with usingtypeof bar === "object"to determine if bar is an object? How can this pitfall be avoided? 老生常谈的问题,用typeof是否能准确判断一个对象变量,答案是否定的,null的结果也是 object,Array的结果也是 object,有时候我们需要的是 "纯...
“Commonly asked JavaScript interview questions“ Comments: TiTiJune 7th, 2011 at 9:46 pm #1. ECMAScript = Define various detailled specs Javascript = The language, general word Jscript = A Microsoft implementation (please don’t ask more :-p) #2. Boolean Number String Date Object? (after a...
Common JavaScript coding interview questions Some of the common JavaScript coding interview questions typically cover these topics: checking for palindrome, finding missing/largest numbers, object manipulation, removing duplicates, merging, etc.1. Write a function to check if a given string is a palin...
object symbol (ES6的新语法) Q9: 请解释事件冒泡以及如何阻止它? 话题: JavaScript难度: ⭐⭐ 事件冒泡的概念是指:在最内层的元素上绑定的事件被触发后,会按照嵌套的层次由内向外逐步触发。因此,点击某个孩子节点可能会触发父节点的事件。 一个阻止事件冒泡的办法就是使用event.stopPropagation(),在IE<9的浏览...
委托（即原型链）。串联（即 mixins，Object.assign()）。函数式（不要与函数式编程混淆。用于为私有状态/封装创建闭包的函数）。每种类型的原型继承都有自己的一组用例，但它们在启用组合方面同样有用，组合创建了has-a或uses-a或can-do关系，而不是 is -a关系使用类继承创建。“对象组合优先于类继承”是什么...
50+ Essential Javascript Interview Questions to Prepare for Your Next Interview JavaScript is an object-oriented scripting language that has evolved from a means to manipulate static HTML and CSS websites into the backbone of today’s most dynamic and interactive websites. Its popularity has ...
原型链查找:如果在对象本身中找不到该属性,JavaScript 将查看该对象的原型(由 __proto__ 属性引用)并在那里搜索该属性。此过程在原型链上递归地继续,直到找到属性或查找到达 Object.prototype。 如果即使在 Object.prototype 中也找不到该属性,JavaScript 将返...
// The Ugly: Really unexpected results [] + {} // "[object Object]" {} + [] // 0 (JavaScript interprets {} as an empty block!) JavaScript Best Practices for Interview and Production Code: When writing code for interviews or production, following these practices demonstrates your unders...