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Data Structures and Algorithms in JavaScript

Q: Does JavaScript have a built-in heap or priority queue?

No. You get Array, Map, Set and their weak variants, and that is all. In an interview you either write a small binary heap, about thirty lines, or say you would use one and state its costs; either way you need to have written one before. Step two of this path is where you do.

Q: Why does [10, 9, 1].sort() return [1, 10, 9]?

Because without a comparator Array.prototype.sort converts the elements to strings and compares them in UTF-16 order, and '10' comes before '9'. Sort numbers with nums.sort((a, b) => a - b). It is the first bug most people meet when they start writing sorting code in JavaScript.

JavaScript gives you Array, Map and Set, and no queue, heap, linked list or tree, so interviews ask you to build them. This path has you write each one in JavaScript, then sort, recurse and search graphs with them, and finish on graded interview problems. Free, in your browser, with a certificate on most courses.

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377 lessons228 challenges702 quiz questions

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DSA in JavaScript, step by step

38 courses377 lessons228 challenges702 quiz questions

Each step is a set of existing Coddy courses, and every Start button opens them in JavaScript. The three courses not taught in JavaScript yet are listed after the steps.

1
Step 1
Data Structures Series, part one
Start this stepStartStack, queue, binary tree, hash table and linked list, each built from scratch in JavaScript and then used to solve problems. After it, you know when an array makes a good stack, when it makes a poor queue, and what Map does for you.Start
5 courses, in order
66 lessons34 challenges
2
Step 2
Data Structures Series, part two
Start this stepStartDoubly linked list, heaps and priority queues, tries, graphs and the self-balancing AVL tree: the structures JavaScript does not ship, written by hand. The heap you write here is the one you reach for in the graph step.Start
5 courses, in order
72 lessons42 challenges
3
Step 3
Sorting algorithms
Start this stepStartBubble, selection, insertion, merge, quick, heap, counting and radix sort, written in JavaScript and watched in the visualizer. The built-in sort() has been required to be stable since ES2019, and V8 implements it as Timsort; after this step you know what both mean.Start
8 courses, in order
74 lessons31 challenges319 questions
4
Step 4
Recursive thinkingDedicated page
Start this stepStartRecursion challenges in JavaScript. Dynamic programming (taught in Python) and bit manipulation (taught in C++) are listed after the steps: a recurrence reads the same in any language, and JavaScript has the same bitwise operators, applied to 32-bit integers.Start Dedicated page15 lessons15 challenges
5
Step 5
Graph algorithms
Start this stepStartBreadth-first and depth-first search, Dijkstra, Bellman-Ford, topological sort, Kruskal and Prim in JavaScript, on the graph you built in step two. JavaScript has no priority queue, so the heap from step two is the one Dijkstra needs.Start
7 courses, in order
63 lessons21 challenges383 questions
6
Step 6
Interview practice
Start this stepStartTen interview challenge packs and two coding-problem banks, all twelve in JavaScript and graded by test cases: unfamiliar problems, solved without a tutorial. The Python interview series, Python only, is listed after the steps.Start
12 courses, in order
87 lessons85 challenges

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Intro to Variables

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A variable is a named container that stores a value you can reference later in your program.

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Why learn DSA in JavaScript on Coddy

The structures JavaScript left out. There is no built-in heap, priority queue, linked list or tree, so implementing one is a staple of JavaScript interviews. On this path you write every one of them, then use them in the graph and interview courses.
Interview prep for web developers. Frontend and full-stack loops at larger companies include algorithm rounds, and frontend candidates usually take them in JavaScript. The DOM is a tree and a component hierarchy is one too, so the same traversals turn up in UI questions.
Nearly the whole path in JavaScript. Every data structure, sort, graph algorithm, recursion challenge and interview pack is taught in JavaScript. The three that are not, dynamic programming and the Python interview series (Python) and bit manipulation (C++), are listed after the steps with their language.
Graded like an interview. Every lesson ends in a JavaScript challenge checked by test cases, and when one fails, Bugsy reads your code and nudges you toward the fix without handing over the answer. A free certificate on most courses, each verifiable at its own URL.

Frequently asked questions about DSA in JavaScript

Is JavaScript good for data structures and algorithms?

Yes, especially if you are heading for frontend or full-stack roles, where it is the language you will interview in. Three quirks are worth learning early: there is no built-in heap or queue, sort() compares as strings unless you pass a comparator, and every number is a 64-bit float, so integers beyond 2^53 need BigInt.

Does JavaScript have a built-in heap or priority queue?

No. You get Array, Map, Set and their weak variants, and that is all. In an interview you either write a small binary heap, about thirty lines, or say you would use one and state its costs; either way you need to have written one before. Step two of this path is where you do.

Why does `[10, 9, 1].sort()` return `[1, 10, 9]`?

Because without a comparator Array.prototype.sort converts the elements to strings and compares them in UTF-16 order, and '10' comes before '9'. Sort numbers with nums.sort((a, b) => a - b). It is the first bug most people meet when they start writing sorting code in JavaScript.

Do frontend interviews ask data structures and algorithms?

At many larger companies, yes: usually one or two rounds of arrays, hash maps, trees and graph traversal, in JavaScript, beside the UI and system design rounds. Smaller companies lean more on practical tasks. Either way, knowing that a Map lookup is constant time and a nested loop over two lists is not is what separates a working answer from a fast one.

Which courses on this path are not taught in JavaScript?

Three: dynamic programming and the Python interview series are taught in Python, and bit manipulation in C++. They are listed after the steps, each with a link that opens it in its own language. JavaScript has the same bitwise operators, plus >>>, but applies them to 32-bit integers, which is worth remembering when you port a trick.

Do I need to know JavaScript before starting this path?

Functions, arrays, objects and classes, at least. If those are new, Coddy's JavaScript course covers them first, free, and this path picks up where it ends.

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