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YusufAdel
YusufAdel

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15 web developer interview questions...

Advanced Interview Questions

The following will cover the senior web developer interview questions but I suggest you go through them even if you are a fresher or an intermediate web developer candidate.

What are the types of popup boxes present in JavaScript?

There are three types of dialog boxes, which are used in JavaScript:

  • Alert: Presents users with a message and an ‘Ok’ button
  • Confirm: Gives the users a window with ‘Ok’ and ‘Cancel’ buttons
  • Prompt: Shows the user input, alongside ‘Ok’ and ‘Cancel’ buttons

What is the difference between and ?

The <window.onload> event is not called until a page is completely loaded with the entire styling from CSS and images. The event does add a bit of delay when rendering a web page.

With the <onDocumentReady> event, it will wait only till the DOM is initialized and will begin the event action. This ensures to reduce any delays in actions.

How is type conversion handled in JavaScript?

JavaScript supports automatic type conversion. Since it is weakly typed, you can pass a function as an argument into another function easily.

This ensures that there are no errors or data type-associated warnings as values get converted to the required data type automatically.

What is the meaning of the scope of a variable in JavaScript?

Scope refers to the accessibility of functions and underlying variables in the running environment. There are two scopes supported in JavaScript:

  • Local scope: Here, values and functions declared inside the same function function can only be accessed within that function and not outside it. Consider the following example:
// Code present here cannot use localVariable
function myFunction() {
var localVariable = "This is a local variable";
// Code present here can use localVariable
}
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  • Global scope: If a variable is declared as global, it can be accessed from anywhere in the application. Consider the following example:
var globalVariable = "This is a Global variable";
// Code present here can use globalVariable
function myFunction() {
// Code present here can also use globalVariable
}
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How are comments used in JavaScript?

JavaScript supports two types of comment insertion in the code. Single-line comments and multi-line comments.

Single-line comment: “//” is used for single-line comment insertion
Example:

//This is a single-line comment

Multi-line comment: /* */” is used to add multi-line comments
Example:

/* This
is a
multi-line
comment*/
`
Coming to the next set of interview questions for web developers, here is a common question for JavaScript.

What are undefined and undeclared variables in JavaScript?

Variables that have been declared already but not initialized are known as undefined variables.

On the other hand, if a variable is being used in a program without being declared, then it is considered as an undeclared variable.

Consider the following example:

var undefVar;
alert(undefVar); // undefined variable
alert(notDeclared); // accessing an undeclared variable

What is the method used to submit forms in JavaScript?

Forms can be submitted easily in JavaScript by calling the following method:

document.forms[0].submit();
Here, the ‘0’ denotes the index of the form.

Why is keyword used a lot in JavaScript?

The <this> keyword is used to access the current object present in a program. This object resides inside a method, and the keyword is used for referencing the corresponding variable or object.

What is the use of the ‘defer’ attribute in JavaScript?

The attribute is used as a boolean type attribute. It is used to delay the execution of the JavaScript code on a web page until the parser completely loads and initializes the page.

Example:

<script src="/example.js" defer></script>

How can you prioritize SEO, maintainability, performance, and security in a web application?

This is a commonly asked question in a Web Development interview. Here, the interviewer is trying to assess your understanding of the working environment in the firm you’ve applied for.

If it is a large firm, then security will get higher priority over SEO. Whereas, if it is a publication firm, SEO gets the preference. A little groundwork about the company should help you answer this question.

The next web developer interview question we will look at is regarding jQuery. Check it out.

What is the result if a jQuery Event Handler returns false?

If the jQuery Event Handler returns a boolean false value, it simply means that the event will not execute further and will halt the execution for the particular action it is associated with.

What is the use of the each() function in jQuery?

The each() function in jQuery is used to iterate over a set of elements. A function can be passed to the each() method. This will result in the execution of each of the events for which the object has been called.

What is pair programming?

Pair programming is a scenario where you will be working closely with a colleague on the project, and this is done to help solve the problems at hand. If the development scenario is fast-paced, Agile development might not work efficiently. The interviewer asks this question to see if you can work with other people easily and effectively.

What is the use of the $() function in jQuery?

The $() function is used as a wrapper to wrap objects into their jQuery counterparts. This is done to give users the ability to call any method that is defined for the jQuery object.

Note: Selectors can also be passed to the $() function, resulting in the output of a jQuery object that contains matched DOM elements.

What are the advantages of using a content delivery network (CDN) in jQuery?

CDNs are widely used in jQuery as they offer an ample number of advantages for users.

CDNs cause a significant reduction in the load for the server.
They provide large amounts of savings in the bandwidth.
jQuery frameworks load faster due to optimizations.
CDNs have a caching ability that adds to quicker load times.

Extra Question:

What are the types of CDNs supported in jQuery?

There are two widely used CDNs with jQuery:

Microsoft: Used to load from jQuery AJAX CDN
Google: Used to load jQuery from the Google libraries API

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Discussion (1)

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devfranpr profile image
DevFranPR

The post is good but some titles are incomplete . Maybe is a code in title thing idk but hopes it help.