Java script interview questions. News, Tips, and Advice for Technology Professionals 2018-09-27

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java script interview questions

JavaScript's this keyword normally refers to the object that owns the method, but it depends on how a function is called. Timers can be tricky to use since they operate within a single thread, thus events queue up waiting to execute. This is accomplished with the setTimeout, setInterval, and clearInterval functions. What is a drawback of JavaScript timers? Do you have a JavaScript framework preference? JavaScript is smart, so it easily determines what the type should be. One application of this is the creation of one event listener on a page's body element to respond to any click event that occurs within the page's body. The var keyword is used to declare a local variable or object, while omitting the var keyword creates a global variable.

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java script interview questions

The value of a variable with no value is undefined i. When working within a Web page, this usually refers to the Window object. How are errors gracefully handled in JavaScript? The clearInterval id function is used to stop a timer. The types supported in JavaScript are: Number, String, Boolean, Function, Object, Null, and Undefined. Plus, the interviewee might introduce you to something you've never used.

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java script interview questions

Most JavaScript developers avoid globals. The big difference is the latter uses coercion, which can have some — it returns true for a null or undefined comparison if they are either. Global variables are available throughout your code: that is, the variables have no scope. Basically, it points to the currently in scope object that owns where you are in the code. This allows you to properly handle code syntax errors and runtime exceptions. There are the vastly popular frameworks like , although you might be surprised when the person tells you about the framework they developed or even played the contributor role.

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java script interview questions

How do JavaScript timers work? The setInterval function, delay function is similar to the setTimeout function except that it executes repeatedly on the delay and only stops when cancelled. One reason why is they're averse to naming conflicts between local and globals, Also, code that depends on globals can be difficult to maintain and test. Unlike Java or C , JavaScript is a loosely-typed language some call this weakly typed ; this means that no type declarations are required when variables are created. The depth and focus of an interview will depend on the position's requirements, so you can choose to go further with some questions or avoid topics based on your needs. Strings and numbers can be intermixed with no worries.

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java script interview questions

Variables can be emptied by setting their value to null. This open-ended question has the potential to spawn a good conversation. From my perspective, I want developers who will use whatever is available to meet a project's demands. The answer to the second question gives you an idea of the candidate's feelings about open source well, that is the way I see it. What are your thoughts on using frameworks? } You can give bonus points to any candidate who discusses the onerror event handler tied to the Window object in the browser — this allows it to monitor all errors on a page. Timers allow you to execute code at a set time or repeatedly using an interval. The setTimeout function, delay function initiates a timer that calls a specific function after the delay; it returns an id value that can be used to access it later.

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java script interview questions

There are so many open source options available today , , , etc. If you are in an object created with the new keyword, the this keyword refers to the object being created. Can you explain how inheritance works in JavaScript? Local variables scope, on the other hand, is restricted to where it is declared like within a function. These open source options provide robust code that has been thoroughly tested by an army of developers. When the time comes to hire JavaScript developers, the following interview questions and talking points might help. These approaches allow multiple developers to work on a project without stepping on their coworkers' toes.

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java script interview questions

In addition, testing modular code or classes is easier to approach than a jumbled mess of code thrown together look around the Web, and you'll find plenty of examples. . The key concept here is to get an idea of how the candidate maintains and designs code. This is the same way it works in other languages like C and Java. For many years, the language was shunned by self-proclaimed real developers, but there has been an about-face within the industry, with JavaScript now viewed as a major vehicle for building powerful Web applications and beyond think. Do they design code that is specific to an application with no possible reuse? My first adventures in Web development were brightened with the introduction of anybody remember? Note: This content is also available as a.

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java script interview questions

What are the problems with using globals? When working with event handlers, JavaScript's this keyword will point to the object that generated the event. Do they use class inheritance or the module pattern to build reusable code? I hope these questions will stimulate a discussion that gives you a peek into what the candidate knows and how the person works. . . . . .

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java script interview questions

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