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Visualization of C++ data structures in the browser.
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MyDataStructures is a collection of basic data structures written in the C++ programming language, and a web interface that allows you to visualize them and interact with them.

Live demo available at

The C++ data structures are compiled into JavaScript using Emscripten and executed in the browser.

The web interface is built using Ember and Bootstrap.


In order to build the Unix binaries GNU Make and Clang are required. (Alternatively you can build the binaries using GCC, but you need to set the CXX variable to g++ in common/Makefile.)

To build the website you need the Emscripten SDK, Node.js and NPM installed and in your path.

Building the Unix binaries

Run make clean all from the root directory.

Building the static website

Install the Broccoli compilation library's command line interface.

cd website
npm install -g broccoli-cli

Then run make website from the project's root directory. This both compiles the data structures into JavaScript and builds the website.

You can then run the website either by opening the website/dist/index.html file in a web browser or by running make serve from the project's root directory and visiting http://localhost:4200.

Adding a new data structure

Follow the steps below.

  1. Create a new directory on the project's root, e.g. foo.
  2. Add the directory you just created to the DIRS variable in the Makefile, e.g. DIRS = avl heap skiplist foo.
  3. Create an empty Makefile inside the newly created directory, define a BIN variable with the desired target binary name, then include common/Makefile. Check out the Makefile in the directory of any data structure for an example.
  4. Add your source code to the new directory.
  5. Define the data structure's JavaScript interface inside a #ifdef EMSCRIPTEN conditional block, as explained shortly below.
  6. Define your Unix binary's main function in an #else block following the previous #ifdef to make sure it's not included in the JavaScript build.
  7. Add a new entry for your data structure in website/js/config.js as explained below.

Defining the data structure's JavaScript interface

  • Your data structure's JavaScript interface is defined as a collection of functions that take zero or one integer parameter and return void.
  • The function names need to start with a common prefix, e.g. foo_.
  • Additionally, you need to provide a print function that takes zero parameters and returns a string of type const char * containing an ASCII representation of your data structure. This is what the user will see in the output panel. If your prefix is foo_, then the function's name needs to be foo_print. This function will be called by the web interface every time the user performs an operation on your data structure.
  • Your functions must be wrapped inside an extern "C" { ... } block, and you need to write the EMSCRIPTEN_KEEPALIVE macro in your function declarations between the return type and the function name. e.g.:
extern "C" {
  void EMSCRIPTEN_KEEPALIVE foo_insert(int x) {

  void EMSCRIPTEN_KEEPALIVE foo_clear() {

  const char * EMSCRIPTEN_KEEPALIVE foo_print() {

Adding the data structure to website/js/config.js

The website/js/config.js file defines a window.DataStructures array containing an entry for every data structure in the web interface. Each entry needs to be a hash with the following fields:

  • name: The name of the data structure, e.g. 'Foo'.
  • functionNamePrefix: The prefix used in the JavaScript interface function names, e.g. 'foo_'.
  • operations: Array containing an entry for every operation defined in the JavaScript interface. Each entry needs to be a hash with the following fields:
    • type: A string 'integer' if the operation takes an arbitrary integer provided by the user, 'random' if the operation takes an integer to be randomly generated by the web interface, or 'void' if the operation takes no parameters.
    • label: Name of the operation, e.g. 'Insert a new item'.
    • functionName: Name of the function for this operation, not including the function name prefix. For example, if this data structure's functionNamePrefix field is 'foo_' and you defined a function foo_insert in your JavaScript interface, this field should be just 'insert'.
  • files: Array containing the soure code file names you want to display in the web interface, e.g. ['/foo/foo.h', '/foo/foo.cpp'].
  • helpText: String containing a brief introduction to the data structure. This text will be shown on the interface next to the data structure. Arbitrary HTML is allowed here.


MIT licensed.

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