End Developer Junior Front Interview Questions

16,940 end developer junior front interview questions shared by candidates

Given input: // could be potentially more than 3 keys in the object above items = [ {color: 'red', type: 'tv', age: 18}, {color: 'silver', type: 'phone', age: 20} ... ] excludes = [ {k: 'color', v: 'silver'}, {k: 'type', v: 'tv'}, .... ] function excludeItems(items, excludes) { excludes.forEach(pair => { items = items.filter(item => item[pair.k] === item[pair.v]); }); return items; } 1. Describe what this function is doing... 2. What is wrong with that function ? 3. How would you optimize it ?
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Front End Engineer

Interviewed at Meta

3.5
Nov 27, 2017

Given input: // could be potentially more than 3 keys in the object above items = [ {color: 'red', type: 'tv', age: 18}, {color: 'silver', type: 'phone', age: 20} ... ] excludes = [ {k: 'color', v: 'silver'}, {k: 'type', v: 'tv'}, .... ] function excludeItems(items, excludes) { excludes.forEach(pair => { items = items.filter(item => item[pair.k] === item[pair.v]); }); return items; } 1. Describe what this function is doing... 2. What is wrong with that function ? 3. How would you optimize it ?

1. In JavaScript, write a function that takes an array as input that can contain both ints and more arrays (which can also contain an array or int) and return the flattened array. ex. [1, [2, [ [3, 4], 5], 6]] => [1, 2, 3, 4, 5, 6] 2. Using HTML and CSS, show how you would create an image that would display another image (aligned to the bottom, right) when the user hovers over the image. ex. The Facebook "edit profile picture" icon
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Front End Engineer

Interviewed at Meta

3.5
Feb 21, 2014

1. In JavaScript, write a function that takes an array as input that can contain both ints and more arrays (which can also contain an array or int) and return the flattened array. ex. [1, [2, [ [3, 4], 5], 6]] => [1, 2, 3, 4, 5, 6] 2. Using HTML and CSS, show how you would create an image that would display another image (aligned to the bottom, right) when the user hovers over the image. ex. The Facebook "edit profile picture" icon

// Given var endorsements = [ { skill: 'css', user: 'Bill' }, { skill: 'javascript', user: 'Chad' }, { skill: 'javascript', user: 'Bill' }, { skill: 'css', user: 'Sue' }, { skill: 'javascript', user: 'Sue' }, { skill: 'html', user: 'Sue' } ]; getSkills = (endorsements) => { // Result // [ // { skill: 'javascript', user: ['Chad', 'Bill', 'Sue'], count: 3 }, // { skill: 'css', user: ['Sue', 'Bill'], count: 2 }, // { skill: 'html', user: ['Sue'], count: 1 } // ]; } see this image: http://i.imgur.com/UIeB3n4.png
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Front End Developer

Interviewed at LinkedIn

3.8
Jan 8, 2019

// Given var endorsements = [ { skill: 'css', user: 'Bill' }, { skill: 'javascript', user: 'Chad' }, { skill: 'javascript', user: 'Bill' }, { skill: 'css', user: 'Sue' }, { skill: 'javascript', user: 'Sue' }, { skill: 'html', user: 'Sue' } ]; getSkills = (endorsements) => { // Result // [ // { skill: 'javascript', user: ['Chad', 'Bill', 'Sue'], count: 3 }, // { skill: 'css', user: ['Sue', 'Bill'], count: 2 }, // { skill: 'html', user: ['Sue'], count: 1 } // ]; } see this image: http://i.imgur.com/UIeB3n4.png

Write an emitter class: /* emitter = new Emitter(); // 1. Support subscribing to events. sub = emitter.subscribe('event_name', callback); sub2 = emitter.subscribe('event_name', callback2); // 2. Support emitting events. // This particular example should lead to the `callback` above being invoked with `foo` and `bar` as parameters. emitter.emit('event_name', foo, bar); // 3. Support unsubscribing existing subscriptions by releasing them. sub.release(); // `sub` is the reference returned by `subscribe` above */
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Front End Engineer

Interviewed at Meta

3.5
Nov 17, 2016

Write an emitter class: /* emitter = new Emitter(); // 1. Support subscribing to events. sub = emitter.subscribe('event_name', callback); sub2 = emitter.subscribe('event_name', callback2); // 2. Support emitting events. // This particular example should lead to the `callback` above being invoked with `foo` and `bar` as parameters. emitter.emit('event_name', foo, bar); // 3. Support unsubscribing existing subscriptions by releasing them. sub.release(); // `sub` is the reference returned by `subscribe` above */

You are given an array of N elements in the form "property1: value1; property2: value2;...;propertyX: valueX;" for some some N and any X. There is also another array of M elements of the form "property: value". You are supposed to write an algorithm to remove every element in the N length array that has a "property: value" pair in the M length array. The trick is that the most intuitive solution of iterating through the M array and filtering the N array at each element is already written. You must come up with a solution that solves the problem in less than O(NM) time.
avatar

Front End Engineer

Interviewed at Meta

3.5
Oct 17, 2018

You are given an array of N elements in the form "property1: value1; property2: value2;...;propertyX: valueX;" for some some N and any X. There is also another array of M elements of the form "property: value". You are supposed to write an algorithm to remove every element in the N length array that has a "property: value" pair in the M length array. The trick is that the most intuitive solution of iterating through the M array and filtering the N array at each element is already written. You must come up with a solution that solves the problem in less than O(NM) time.

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