![\"JavaScript](\"https:\/\/www.dynamicwebtraining.com.au\/blog\/wp-content\/uploads\/2019\/06\/JS-Feature-1024x536.jpg\")
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JavaScript Interview Questions Commonly Asked<\/h2>\n\n\n\n
To help you with that we lay down the questions that are frequently asked. Here are Top 10 JavaScript Interview Questions commonly asked with their answers. <\/p>\n\n\n\n
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Question No.1: What is the difference between \u201clet\u201d and \u201cvar\u201d keyword?<\/h4>\n\n\n\n
Ans:<\/strong> <\/p>\n\n\n\n This is a fundamental question & an interviewer would expect you to answer it. \u201cvar\u201d<\/em><\/strong> & \u201clet\u201d<\/em><\/strong> are used for the function declaration, but they differ in scope. <\/p>\n\n\n\n Ans: <\/strong><\/p>\n\n\n\n Undefined <\/em><\/strong>is a keyword without any assigned value. While null <\/em><\/strong>is just an assignment value, the programmer can assign a null value to any keyword. Both are two distinct types; typeof(undefined)<\/em><\/strong> remains undefined whereas typeof(null)<\/em><\/strong> becomes an object. <\/p>\n\n\n\n There\u2019s another dimension to this question as follows:<\/p>\n\n\n\n Ans:<\/strong> <\/p>\n\n\n\n “==”<\/em><\/strong> compares value of both sides. Here, undefined<\/em><\/strong> & null<\/em><\/strong> both have empty values or no values. Therefore, the comparison is true. Meanwhile, undefined ===<\/em><\/strong> null is false because “===\u201d<\/em><\/strong> (strict equality operator) compares type & value. So, undefined remains undefined but null becomes object.<\/p>\n\n\n\n Example:<\/strong><\/p>\n\n\n\n Ans: <\/strong><\/p>\n\n\n\n Ans:<\/strong><\/p>\n\n\n\n Elements can be retrieved using JavaScript by following functions:<\/p>\n\n\n\n Ans:<\/strong><\/p>\n\n\n\n Object Seal:<\/strong><\/p>\n\n\n\n Object Freeze:<\/strong><\/p>\n\n\n\n Ans: <\/strong><\/p>\n\n\n\n IMPORTANT<\/strong> Easier Explanation: <\/strong><\/p>\n\n\n\n In JavaScript, by default, each function has a particular property known as \u201cPrototype.\u201d By default prototype is empty. However, we can add methods & properties in it. Suppose there\u2019s a function \u201cJ.\u201d And its prototype has methods & properties in it. Now, if we create an object using \u201cJ” say J1. J1 will inherit properties & methods from \u201cJ.\u201d This type of inheritance is known as \u201cPrototypal Inheritance.\u201d<\/p>\n\n\n\n Ans: <\/strong><\/p>\n\n\n\n Function declaration & function expression are two different entities. The major difference is \u201cHoisting<\/strong><\/em>\u201d & \u201cSyntax<\/strong><\/em>\u201d. <\/p>\n\n\n\n Ans:<\/strong><\/p>\n\n\n\n As the name says, PROMISE<\/em><\/strong> represents a value that is not present but will be available in the future. A promise represents asynchronous code operations. Programmers use Promise as an alternative of composing, executing or handling asynchronous operation instead of call-back operations. It is easier to handle such operations using Promise because it provides approaches similar to synchronous catch\/try. <\/p>\n\n\n\n Phases\/States of Promise:<\/strong> Ans: <\/strong><\/p>\n\n\n\n Ans: <\/strong><\/p>\n\n\n\n Scripts can be written in 2 sides; Client & Server. The significant difference between server-side & client-side is \u201cback end.\u201d In server-side, there\u2019s involvement of server whereas in client-side it requires browser on the user end. <\/p>\n\n\n\n Client-Side JavaScript:<\/strong><\/p>\n\n\n\n Server-Side JavaScript:<\/strong><\/p>\n\n\n\n Few more important topics you should not miss :<\/p>\n\n\n\n These questions are subjective. From an interviewer\u2019s perspective, they might expect you to answer such questions. This compilation covers the top 10 irrespective of its depth or complexity. In the end, there are few key\/crucial terms an individual should know for a JS Interview. That\u2019s all! Best of luck!<\/p>\n","protected":false},"excerpt":{"rendered":" Interviews are often unpredictable, and when it comes to programming, it is even trickier. JavaScript interviews can be overwhelming as the subject is vast and you won\u2019t know which questions can deceive you. If you plan well then there\u2019s nothing to be anxious about.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1621],"tags":[],"class_list":["post-1282","post","type-post","status-publish","format-standard","hentry","category-programming"],"yoast_head":"\n
\n\n\n\nQuestion No.2: What is the difference between \u201cundefined\u201d & \u201cnull\u201d keywords?<\/h4>\n\n\n\n
\n\n\n\nHow is undefined==null true?<\/h4>\n\n\n\n
\n\n\n\nundefined == null \u2014\u2014> True\nundefined === null \u2014\u2014> False<\/code><\/pre>\n\n\n\n
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\n\n\n\n\u20181\u2019 == 1 --\u2014> True\n\u20181\u2019 === 1 --\u2014> False<\/code><\/pre>\n\n\n\n
\n\n\n\nQuestion No.3: State difference between ViewState & SessionState?<\/h4>\n\n\n\n
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\n\n\n\nQuestion 4: How to access elements using JavaScript?<\/h4>\n\n\n\n
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\n\n\n\nQuestion 5: What do you mean by Object.freeze & Object.seal?<\/h4>\n\n\n\n
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\n\n\n\nQuestion 6: What is prototypal inheritance?<\/h4>\n\n\n\n
JavaScript objects have the hidden property known as “[[prototype]].\u201d. This prototype refers to an object or its null. Such objects are known as a prototype. To understand prototypal inheritance lets consider an example. Suppose we want to read\/view property of an object, but it\u2019s missing. JavaScript by-default calls it from the prototype. Inheritance of properties by default is known as \u201cPrototypal Inheritance.\u201d <\/p>\n\n\n\n
\n\n\n\n![\"Prototypal](\"https:\/\/www.dynamicwebtraining.com.au\/blog\/wp-content\/uploads\/2019\/06\/js-prototypal-inheritance.jpg\")
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\n\n\n\nQuestion 7: What is the difference between function declaration & function expression?<\/h4>\n\n\n\n
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Function expression syntax : anonymous function (like let, var, etc) function name()<\/li>\n\n\n\n
Function expression: defines a function & can be stored in a variable.<\/li>\n\n\n\n
\n\n\n\nQuestion 8: What is promise & why do we use it?<\/h4>\n\n\n\n
Pending:<\/em> Asynchronous operation not completed
Fulfilled :<\/em> Operation synchronized & value determined
Rejected: <\/em>Operation failed!<\/p>\n\n\n\n
\n\n\n\nQuestion 9: What is Regular Expression (regExp)?<\/h4>\n\n\n\n
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\n\n\n\nQuestion 10: What is the difference between Client-side & Server-side JavaScript?<\/h4>\n\n\n\n
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\n\n\n\nConclusion:<\/h4>\n\n\n\n