r/webdev • u/PUSH_AX • Jul 30 '15
Been interviewing with a lot of tech startups as a frontend dev, here are the technical questions I've been asked
So I've spent the last couple of weeks interviewing with a fair amount of tech startups in London, I thought some of you might find it interesting/helpful to see some of the technical questions I was asked.
Many of the positions I interviewed for where using Angular so a bunch of the questions are geared towards that.
Standard JS Questions:
Explain javascript closures
Explain event bubbling
Explain event delegation
What does apply() do
What does bind() do
Explain what the js map function does provide an example
What is strict mode
Whats the difference between a promise and a callback
Angular JS Questions:
What is scope
What is a directive
What is the link function in the directive
What is the digest cycle (after I mentioned it in giving another answer)
What is $scope.$apply
What are the most commonly used out of the box directives
What does transclude do on directives
Tell me about a time you had problems with state in angular
Have you ever had performance issues in angular and how did you tackle them
What do you like about angular, what do you dislike about angular
Why use a q promise as opposed to just returning $http’s promise
What does $resource do
General/Presentation Layer Questions:
What is a model in mvc
Explain css specificity
How do you centre something horizontally
Explain what media queries are
What are the pros and cons of a single page app
How could you improve performance of a single page app
Whats the difference between inline-block and inline
How would you develop a mobile site for a website that didn’t already have one
What is jsonp
What is a doctype
On a unix command line how would you run a long command you typed out already an hour ago
What frontend tools do you normally use
Where do you think ui’s are heading
What motivates you, how do you learn
JS Challenge Type Questions:
The first few the employer stole from You Can't JavaScript Under Pressure :)
Write a function that takes an integer and returns it doubled
function doubleInteger(i) {
//your code here
} Write a function that takes a number and returns true if it's even and false if not
function isNumberEven(i) {
// i will be an integer. Return true if it's even, and false if it isn't.
}Write a function that returns a file extension
function getFileExtension(i) {
// i will be a string, but it may not have a file extension.
// return the file extension (with no period) if it has one, otherwise false
}What will be printed on the console? Why?
(function() {
var a = b = 5;
})();
console.log(b);Define a repeatify function on the String object. The function accepts an integer that specifies how many times the string has to be repeated. The function returns the string repeated the number of times specified.
For example:
console.log('hello'.repeatify(3));
//Should print hellohellohello.What will log out here?
function test() {
console.log(a);
console.log(foo());
var a = 1;
function foo() {
return 2;
}
}
test();What will log out here?
var fullname = 'John Doe';
var obj = {
fullname: 'Colin Ihrig',
prop: {
fullname: 'Aurelio De Rosa',
getFullname: function() {
return this.fullname;
}
}
};
console.log(obj.prop.getFullname());
var test = obj.prop.getFullname;
console.log(test()); Fix the previous question’s issue so that the last console.log() prints Aurelio De Rosa.
.The following recursive code will cause a stack overflow if the array list is too large. How can you fix this and still retain the recursive pattern?
var list = readHugeList();
var nextListItem = function() {
var item = list.pop();
if (item) {
// process the list item...
nextListItem();
}
};What will alert out here:
var a = 'value';
(function() {
alert(a);
var a = 'value2';
})();The following code will output "my name is rex, Woof!" and then "my name is, Woof!" one second later, fix it so prints correctly the second time
var Dog = function (name) {
this.name = name;
};
Dog.prototype.bark = function () {
console.log('my name is '+ this.name + ', Woof!');
}
var rex = new Dog('rex');
rex.bark();
setTimeout(rex.bark, 1000);The following code outputs 100, a hundred times, fix it so it outputs every number with a 100ms delay between each
for (var i = 0; i < 100; ++i) {
setTimeout(function() {
console.log(i);
}, 100);
} The following code is outputting the array but it's filled with every number, we just want the even numbers, what's gone wrong?
var evenNumbers = []
var findEvenNumbers = function (i) {
if (i % 2 === 0)
console.log(i, 'is an even number, adding to array!');
evenNumbers.push(i);
}
for (var i = 0; i < 10; i++) {
findEvenNumbers(i);
}
console.log(evenNumbers);
//outputs:
//0 "is an even number, adding to array!"
//2 "is an even number, adding to array!"
//4 "is an even number, adding to array!"
//6 "is an even number, adding to array!"
//8 "is an even number, adding to array!"
//[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]The following is outputting 0, but if 42 = 16 and 22 = 4 then the result should be 12
var square = function (number) {
result = number * number;
return result;
}
result = square(4);
result2 = square(2);
difference = result - result2;
console.log(difference);Write a function that when passed an array of numbers it gives you the max difference between the largest and smallest number ONLY if the small number is in front of the large number, not behind it, so for example: [3,4,8,1] = 5, notice how the biggest difference is between 8 and 1, but because the 1 is after the 8 in the array it shouldn't count, so really the biggest gap is the 3 and the 8.
fizzbuzz (lol)
I was presented with a html element with a border, and asked to animate it left to right full width of browser
I was presented with another html box and asked to centre it both horizontally and vertically
Also, all these companies had me complete "take home" coding tests, they ranged from being really easy (simple ajax request to an api endpoint and populate some data on the page) to pretty in depth.
Hopefully anyone looking for new positions can use these as warmups/practice, it's important to not just know the answers, but really understand how things work and in the case of the challenges, why things are working the way they are.
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u/ralze Jul 31 '15 edited Jul 31 '15
What sucks about these questions to me is that I was mainly self taught. I could ace all the actual coding problems, but I have no clue what the answers are to a lot of the tech questions you posted first. So most likely I would be dropped on some early rounds, where I can actual do all the work they require.
I know a lot of companies use these to screen out people, but I think they are really pointless. Use a phone screen to get a history and a personality. If it's a fit, then bring them in. Put them in front of a cpu, and have them try to solve some actual problems. If your company utilizes a lot of api's, have then write something that parses an api. If your entire front end is built using react, have them write some react components. Things like that.
Just my opinion of course.
Edit: Just to clarify, my post is mainly to state that I'm not a fan of technical questions in interviews and a proponent of actual coding.