Top 25 jQuery Interview Questions ? And How To Answer Them


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JavaScript development experience is one of the most popular and in-demand skills today, for building and maintaining websites. Coding Dojo estimates that JavaScript is utilized by over 80% of web developers, and is prevalent in 95% of all websites. This places JavaScript skills high on the list for technical recruiters.

Once you?re proficient with coding in JavaScript, you can enhance your skills and marketability significantly by learning and mastering jQuery. According to Gooroo, the average salary for a jQuery developer is over $85,000 ? certainly a skill worth pursuing whether you?re a freelancer or looking for a long-term engagement as a full-time developer.

What Is jQuery?

Jquery Logo

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jQuery is a library of JavaScript functions that makes life easier for JavaScript developers. jQuery enables developers to execute common tasks with a single line of jQuery code, that replaces what could be many lines of JavaScript.

jQuery supports all popular browsers, and is utilized by companies with some of the largest presence on the web:

  • Google
  • Microsoft
  • Netflix
  • IBM

jQuery is the most prevalent JavaScript library in use today, and is a free, open source library that is invaluable to developers with its many capabilities and uses

  • Simplifies HTML scripting
  • Create animations
  • Simplify navigation of documents and Document Object Model (DOM) elements
  • Handle events
  • Create powerful pages and web apps
  • Even create plug-ins over the JavaScript library

With its own level of function shorthand to promote simplicity and brevity in coding, jQuery enhances the productivity of JavaScript and web page development. This is what makes jQuery experience a very desirable skill for businesses.

Before you can benefit from your jQuery skill set, you need to get past the hurdle of interviewing successfully for the position. So it?s critical to anticipate the questions a potential employer will ask, and the answers they will be looking for.

?jQuery Interview Questions

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As a knowledgeable jQuery developer, you should be ready for and able to answer these questions in an interview:

Name some of the most useful features of jQuery

jQuery can be used by developers to:

  • Provide effects and incorporate animations
  • Apply/change
  • DOM selection events
  • Use of plug-ins
  • Ajax support
  • Event handling

How is the document.ready() function different from body.onload()?

There are 2 significant differences:

  • Document.ready() is called as soon as DOM is loaded. Body.onload () is not called until everything on the page is loaded including images, resources, and DOM. One of the main benefits of document.ready() is that it is functional across all browsers.
  • Only one onload can be present for a page, where multiple document.ready() functions can exist

What are some advantages of using jQuery?

  • jQuery simplifies JavaScript development without the need to learn an entirely new syntaxIt makes code simpler and more understandable
  • Many plug-ins are available for developers to utilize
  • jQuery actually improves the performance of applications
  • Event handling
  • Eliminates the need to code complex routines for DOM scripting and logic loops

What are jQuery selectors? How do you use them?

  • Selectors allow you to select a single or a group of elements from HTML of a web page
  • jQuery supports all CSS selectors, plus custom selectors
  • Selectors in jQuery always start with the dollar sign and parentheses $()
  • Developers can select elements based on varying criteria:
  • Tag name
  • ID

What are jQuery selectors? How do you use them?

  • Selectors allow you to select a single or a group of elements from HTML of a web page
  • jQuery supports all CSS selectors, plus custom selectors
  • Selectors in jQuery always start with the dollar sign and parentheses $()
  • Developers can select elements based on varying criteria:
  • Tag name
  • ID

In jQuery, these selectors are the same as those you’re used to with CSS.

What is the difference between width() and css(?width?)?

You have two ways to change the width of an element in jQuery. The difference between the two is in the value or data type returned from each function:

When using css(?width?) you must provide the ?px? operand for the width value, where with width() you do not have to pass that value

Using css(?width?) will provide the value ?300px?, but width() returns only the integer value 300

Describe how to create and work with cookies with jQuery

Cookies can be read, created, and deleted with the Dough plug-in

How can you hide an image when a button is clicked in jQuery?

jQuery provides very effective functionality for event handling. When you find an image, using either an ID or class, that you want to hide based on detecting the ?ButtonToClick? event, specifying the hide() option will hide the image specified.

Are there advantages to using the minimized version of jQuery?

Yes ? minimized version of the jQuery js file can be as much as 50% smaller than non-minimized js files, resulting in faster loading of web pages.

Explain the difference between children and find methods in jQuery.

Find method will discover all levels down the DOM tree. Children will find only a single level down the tree.

What is a jQuery connect, and when would you use it?

jQuery connect is actually a plug-in used to connect a function with some other function. You would use jQuery connect when you want to execute a function from some other function or plug-in. You can download jQuery connect from the jQuery website, then use the $.connect function to include the plug-in in your HTML.

What is the purpose of the jQuery load method?

jQuery load function is a method whereby you can load data from a server and assign the resulting data into the desired element without loading the web page. This can improve performance of the application.

Describe the purpose/use of the jQuery filter

jQuery filter can filter the values from an object list based on filter criteria. This could be used, for example, to select employees from certain states from a personnel database.

Is jQuery scripting utilized on the client or server side?

jQuery is scripting on the client side. jQuery code is executed within client browser functions.

Are there performance variations between jQuery selectors?

Yes ? ID and element selectors are the fastest, while class selectors are the slowest.

What is the application of the ?each? function in jQuery?

Each function allows you to loop through all elements of a target object. This can be effective when utilizing multi-element DOM, object properties and looping arrays.

Are you locked into using jQuery?s $ character in your code?

No ? utilizing the ?NoConflict? method, you can replace the $ with a stored variable of your choice.

Is there an easy or designated way to debug jQuery functions?

Yes ? jQuery can be debugged in two different ways with the debugger keyword:

  • Insert a breakpoint after attaching the process
  • Add the debugger function to the line after you want to start debugging, then run Visual Studio in debug mode.

Explain the use of .empty(), .detach(), and .remove()

Remove method is used when you need to remove all the matched elements. This removes all the jQuery data that is associated those matched elements.

Detach functions the same as remove, with the exception that it does not remove the jQuery data associated with the elements.

Empty method removes all the child elements from the matched elements

How would you add an HTML element in a DOM tree?

jQuery element method appendTo() adds an element to a DOM tree. jQuery provides many methods for manipulating DOM content. You can add either a new HTML element or an existing element.

What is jQuery method chaining, and why would you use it?

Calling a method as a result of another method is called method chaining. Method chaining provides easily-read and clean code, and also can provide better performance by providing a single search over a DOM.

What is the difference between the .get() method and the jQuery .ajax() method?

Get() is a specific function over ajax to retrieve data. Ajax() is more configurable and powerful, allowing you to not only specify how long to wait for a response, but also how to handle error conditions.

Can you add or remove CSS classes with jQuery?

Yes ? this is a very handy function of jQuery. By applying the addClass() and removeClass() methods, jQuery developers can dynamically alter the class of elements, such as making them active or inactive.

How would you set an attribute in jQuery?

The jQuery attribute method ? attr() ? will alter the named attribute with the new value specified on the method.

What is the difference between the prop() and attr() methods?

Each method is used to set or get the property of an element?s attribute. The difference is that prop() returns the current value of the property, where attr() returns the default value.

You can retrieve the attribute of any HTML element. Select the links (all links or only specified links) using a jQuery selector then set the attribute as applicable.

What is the jQuery .data() method used for?

The .data() method associates data with JavaScript objects and DOM nodes. This makes code easy to read and understand.

?Getting Started in jQuery Development

As a knowledgeable jQuery developer, you should be ready for and able to answer these jQuery interview questions easily.

If you?re just getting started in jQuery coding, there are courses available online that will not only teach you the basics, but even provide certification, which can give you an advantage to prospective employers.

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