Commonly asked Interview Questions for Front End Developers

1) CSS, JS best practices? Strict mode, etc.

2) Mention some IE CSS issues faced by developers.

3) How to defer an element’s event handler if it depends on an external script that takes some time to load?

4) Optimal strategy for winning a game where let’s say, I start with 1, opponent can cite a number X within the range [2, 11]. Then I have to say a number in the range [X + 1, X + 10], then opponent, then me, and so on. Whoever says 100 in the end wins and the game ends.

5) Why would you use the prototype in JS?

6) How would you design the 2 way binding feature in Angular?

7) What is the meaning of ‘this’ in JS?

8) Namespaces in JS

9) Difference between null and undefined in JS. A function that returns nothing has a return value of undefined.

10) Closures in JS with example of statements in loop

11) JS event loop, promise, etc.

12) AngularJS memory management

13) Hoisting in JS?

14) In the code snippet below,

var request = new XMLHttpRequest();
request.addEventListener('load', function(e) {
     console.log(this.responseText);
     var obj;
     try {
        obj = JSON.parse(this.responseText);
     } 
     catch(ex) {    
     }
  }); 
request.open('GET', 
'http://api.openweathermap.org/data/2.5/weather?q=delhi&APPID=0d84d993b430de4bebaa89bf7513676e');
request.send(); 

15) What is the difference between this and e in the callback in the above code? In general, event could be anything, not just the load event. Interviewee is expected to know the syntax for sending AJAX request using bare JS.

16) Data types in JS?

17) typeof([]) is object.
var b = []; b.v = 10; b.push(11); What are the contents of b? length of b?

18) Different ways to create objects in JS? Explain Object.defineProperty().

19) Scope and execution context in JS?

20) How to implement inheritance in JS?

21) Create private members in JS objects?

22) Function.prototype.call(), bind() and apply()?

23) How are $apply(), $watch(), $digest() different in AngularJS?

24) AngularJS scope life cycle, ng-init, etc.?

25) How does scope bind the model and the view together, internally?

26) Experience with any other JS framework?

27) Sequence in which the browser parses the page?

28) Sequence of steps that happen when a URL is entered in the address bar of the browser?

29) How does JS manage multiple events in parallel, like click, input, etc. when it is interpreted & single threaded?

30) REST concepts. GET, POST, PUT, DELETE

31) Interviewee should be able to add & remove elements in DOM without a library or framework

32) Must use JavaScript Arrays functions

33) Questions on function inside function, related to scope. Difference between var m = 0; & m = 0;

34) Object Oriented JS and JS patterns by Addy Osmani. This one is an advanced topic.

35) Describe the M, V and C in MVC framework.

*AngularJS questions are relevant for those who have used it.

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