What does the instanceof keyword do?

Question

BlackTom AI · Accepted Answer

Here we explore what the instanceof keyword does in JavaScript (and similar languages), by evaluating each option step by step.
Option 1: 'It converts an object to a primitive data type.' This is incorrect. The keyword is not used for type conversion or coercion; that would involve mechanisms like valueOf, toString, or explicit conversions. instanceof does not perform any conversion work.
Option 2: 'It checks if an object belongs to a specific class' This statement is accurate. instanceof tests whether the prototype chain of an object includes the prototype property of a constructor, effectively answering whether the object is instance of that class (or its subclasses). This aligns with how runtime type checks are commonly performed in languages with prototype-based inheritance.
Option 3: 'It is used to create a new instance of a class.' This is incorrect. The creation of a new object instance is done with operators like new, not with instanceof. instanceof merely inspects an existing object’s prototype linkage.
Option 4: 'It is used to declare a new instance variable.' This is also incorrect. Declaring or defining an instance variable is a language feature tied to class definitions and syntax, not something performed by instanceof. The keyword has no role in variable declarations.

What does the instanceof keyword do?

查看解析

登录即可查看完整答案

类似问题

What does the instanceof keyword do?

What type of validation check is shown above?

How would you find the data type of a variable x in Python?

What will the function `(define (test x) (cond ((number? x) "num") ((string? x) "str") ((list? x) "list") (else "other")))` return when `(test "hello")` is called?

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单