UI Developer or User Interface Developer is the person who build User Interface/ Front End of website. To build User Interface of a website , a UI Developer must know HTML, CSS and JavaScript used to build Front End of a website.

UI Interview Questions

UI developer interview questions with answers. UI Development or User Interface Development is the fastest growing profile in IT Sector. If you are looking for latest UI Interview questions with answers, you are at right place. This article includes interview questions on Html5, Css3, JavaScript & Jquery.

Difference between UI and UX

UI means USER Interface and UX means User Experience. UI Is mainly related to look and feel, colors, layout. But UX is related to how UI is used, i.e. usability, wireframing, interaction with UI.

Design of button is UI, but interaction with button is UX.

How to test website performance.

Website performance play a major role. As per Think With Google website, a website is excellent id its loading time is under 5 seconds. A website is fair if loading time is 5 to 8 seconds. But a website is poor if loading time is more than 8 seconds.

website speed test and performance meter

Use of Jquery ready function.

Jquery recommends use of $(document).ready(function(){ }) or $(function(){ }) in script tag to write jquery syntax. Jquery ready function execute jquery functions after all html elements are loaded, before images, Iframes, ads are loaded.

Difference between Jquery ready function and window onload.

window.onload is a javascript function whereas $(document).ready is a Jquery function. Jquery ready function loads content slightly faster than javascript window.onload function. window.onload wait for all DOM contents including media to load first and then executed, whereas Jquery ready function wait for only html elements, not media, thus load fast.

HTML Interview Questions

What is the difference between Xhtml, html 4 and html 5? Which one do you use typically?

XHTML was the cleaner and stricter version of HTML-4. Whereas HTML5 is the latest, smartest, and fastest version of HTML with semantic elements, audio video, forms, APIs and CSS3.

Does HTML needs compiler?

HTML, CSS and JS are browser interpreted technologies. Whereas Asp.net, Java and Php are not interpreted. They need a compiler which can convert their code in machine language. That's why HTML, CSS and Javascript are also called front-end technologies.

What is Semantic HTML?

HTML5 introduced semantic tags like header, nav,article,section, aside, footer and figcaption. These tags convey the containing content. Whereas in html4, div tag was used to create partitions using descriptive classes.

Which is best HTML debugging tool.

We use chrome, firefox and firebug Dev tools as they are browser inbuilt. But W3C Validation is best HTML Debugging tools.

How to use HTML5 New tags in IE8 and lesser.

HTML5 semantic tags like, header, nav,article,section, aside, footer and figcaption are not supported in HTML4 based browsers like IE8 and lesser. We can use html5shiv.js to run these elements in older browsers.
→ See More html5 tags in IE8

What is web accessibility?

Web accessibility means a web for differently abled or disabled people. HTML5 introduced WAI ARIA so that even disable people can interact, understand and navigate a website.

Difference between <b> and <strong> tag?

<b> is a presentational element used to give bolder look to text. Whereas <strong> gives bolder look and strong importance in search results.

Difference between <i> and <em> tag?

<i> is a presentational element used to give italic look to text. Whereas <em> gives italic look and emphasise in search results.

CSS Interview Questions

Difference between reset.css and normalize css?

reset.css removes all build-in browsers styling like, margin, padding and border. But normalize.css gives a common book like appearance, like bold heading, margin between two paragraphs, common font-family, etc.

What is CSS Box Model?

CSS Box Model includes content, margin, padding, and border. Total width is equal to width + padding + margin + border. These properties occupies space on box model.
→ See More CSS Box Model

How to check coding errors in css?

Open your webpage in Firefox. Press Ctrl + shift + j. You will see all security, javascript and css related issues. You can also use W3C validator for HTML and CSS related issues. Even w3c validation can check css errors now.

Difference between display none and visibility hidden ?

Visibility:hidden hide the content from user but retain space. Whereas Display:none hide the content and remove space.

How to center align a div tag in css?

Div is block level element. By default, div occupy 100% width of parent element. To center align a div in css, use

 <div class="wrap"<
     // content for wrap div

Difference between Position Relative, Absolute and Fixed

Position relative can move a element with respect to its current position. Position absolute can move a element with respect to its current position or parent elements position. Absolute Elements doesn't occupy space in DOM Flow. Position fixed gives fixed position to an element with respect to device screen. These elements doesn't move on scrolling. Fixed Elements also doesn't occupy space in DOM Flow.
See More CSS Positions

Javascript Interview Questions

Is JavaScript Case Sensitive?

Yes, Javascript is case sensitive. But HTML and CSS are not.

What is difference between == and === operator?

== is comparison operator, whereas === is hard equality. == checks value only, === check value and datatype. 5=="5" id true, but 5==="5" is false.

What is output of "20" + 20?

"2020". First 20 is string type, second is numeric, for addition, both should be numeric.

What is output of "20" + 20 + 20 and "20" + ( 20 + 20)?

"20" + 20 + 20 = "202020". "20" + ( 20 + 20) is "2040".

How to convert "20" to number?

Three ways to convert string into number

           var x="20";
            Number(x)       //  20 
            parseInt(x)     //  20
            parseFloat(x)   //  20

What is an AJAX request and give a simple example of where an AJAX request would be used.

AJAX is Asynchronous JavaScript and XML. It is client side process to get or post data from remote server without reloading page.

What is Javascript Hoisting?

A variable is declared first and then called. If variable is declared on bottom and called earlier, value will be undefined. Only assigned values are hoisted in Javascript, like string, numbers etc. Undefined and function declaration can be called before declaration as they are not hoisted, and there is no assignment operator (=) in both. JavaScript Variables

Event bubbling and Event Capturing.

Event Propagation are the order that event fire on element. Bubbling is when an event fire on the element and then bubble up DOM Tree. Means First child and then parent will call. Capturing is exactly opposite. First parent node is called and then propagates down towards target element. Event Bubbling and capturing