Performance is arguably the most significant advantage that WebAssembly offers. The main principle here is running code at near-native speed by taking advantage of common hardware capabilities available on a wide range of platforms. WebAssembly achieves this with its binary format that provides smaller download sizes than typical JavaScript files, leading to faster load times.

Let's take a common performance-critical task - image manipulation. If you were to implement an image blurring algorithm purely in JavaScript, it might be satisfactory for small images. However, as the image size increases, you'll start to see the JavaScript engine struggle with the load, leading to slow performance and high CPU usage. Implementing the same functionality in C++ compiled to wasm can result in significant performance gains.

1#include <emscripten/bind.h>
2using namespace std;
3
4void blurImage(int* imageData, int width, int height) {
5  // replace with your C++ logic here
6}
7
8EMSCRIPTEN_BINDINGS(my_module) {
9  emscripten::function("blurImage", &blurImage);
10}

This code would define a blurImage function that you can call from your JavaScript code to blur an image.

When compiled to wasm and loaded into a browser, this function will run at near-native speed, thanks to the efficient wasm binary format, the optimization capabilities of wasm-compatible browsers, and the raw performance of C++.

WebAssembly doesn't aim to replace JavaScript but to work alongside it, providing performance optimizations where necessary. As WebAssembly continues to evolve, we can expect even more impressive performance feats.

xxxxxxxxxx

#include <emscripten/bind.h>

using namespace std;

​

void blurImage(int* imageData, int width, int height) {

  // replace with your C++ logic here

}

​

EMSCRIPTEN_BINDINGS(my_module) {

  emscripten::function("blurImage", &blurImage);

}