Frontend Interview Coding Questions

Front 1

Question: What is the value of foo?

var foo = 10 + '20';

Back 1

foo = "1020";

Front 2

Question: How would you make this work?

add(2, 5); // 7

add(2)(5); // 7

Back 2

var add = function(a, b) {

return a + b;

};

for second function... (https://www.reddit.com/r/javascript/comments/2t6riw/a_frontend_developer_interview_question_thats/)

Front 3

Question: What value is returned from the following statement?

"i'm a lasagna hog".split("").reverse().join("");

Back 3

"goh angasal a m'i"

Front 4

Question: What is the value of window.foo?

( window.foo || ( window.foo = "bar" ) );

Back 4

it is a check to see if a foo function exists in the window. if it doesn't, then set it to "bar"

Front 5

Question: What is the outcome of the two alerts below?

var foo = "Hello";

(function() {

var bar = " World";

alert(foo + bar);

})();

alert(foo + bar);

Back 5

first alert: "Hello World";

second alert: ReferenceError, bar not defined

Front 6

Question: What is the value of foo.length?

var foo = [];foo.push(1);foo.push(2);

Back 6

foo.length = 2;

Front 7

Question: What is the value of foo.x?

var foo = {n: 1};

var bar = foo;

foo.x = foo = {n: 2};

Back 7

foo.x = undefined

setting foo.x = foo is resetting the value of foo all together, so foo.x no longer exists on the new foo

(http://stackoverflow.com/questions/32342809/javascript-code-trick-whats-the-value-of-foo-x)

Front 8

Question: What does the following code print?

console.log('one');

setTimeout(function() {

console.log('two');

}, 0);

console.log('three');

Back 8

"one";

"three";

"two";

the callback provided (setTimeout) is queued, even if the delay specified is zero.