JavaScript Interview Questions [StartupCTO]

Last Updated: 12 Jul 2026

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Author: 49.151.111.153

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= JavaScript Interview Questions =

== Basic JavaScript ==

 * Give a high level overview of how JavaScript interacts with the DOM.
 * What are some different ways that JavaScript code can be embedded into or linked into an XHTML page?
 * Are objects passed by value or by reference? Does the type of object matter?
 * Is JavaScript an object-oriented language? Why or why not?
 * What is your favorite way to debug JavaScript?
 * What is JSON? What are some common uses of JSON?
 * What is the difference between ''undefined'' and ''null''?
 * What does the ''isNaN()'' function do?
 * What will the following code do? <code javascript>
function printMe() { var b = 5; alert (a+b); }
var a = 3; var b = 2;
printMe();
alert(a+b);
</code>
 * What is a ''for...in'' loop?
 * What is the difference between window.onload and onDocumentReady? Which are you (typically) more likely to use?
 * What are a few different ways to attach handlers (e.g. click, blur, etc.) to a DOM element? Are any better than the others?
 * What's unique about functions in JavaScript? (The answer you're looking for here is that they're first class objects; e.g. you can pass a function as an argument to another function, just like you could pass an object. Explore this concept with the interviewee to see how much they know.) 
 * What's an anonymous function?
 * What is JavaScript namespacing? Why would you want to use it?

== jQuery ==
 * Basic: what is jQuery?
 * How do you select a DOM element (or elements) in jQuery?
 * What does it mean to chain functions in jQuery?

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