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Webassembly Learning Note


1. how to write an typescript funciton add(a: number, b: number) : number function in webassembly and output the log from tavascript side

Typescirpt side:

const consoleLog = {
  console: {
    log: () => {
      console.log('typescirpt side log')

Wasm side add.wasm:

  (import "console" "log" (func $consolelog))
  (func $add (param $a i32) (param $b i32) (result i32)
      call $consolelog // will output typescirpt side log
      local.get $a  //local used to declare a new local variable, we can use local $x i32 to create a local variable x, or local.set $x (i32.cnost 10) to change the local variable to 10. in this example, it will load param $a onto the stack.
      local.get $b
  (export "add" (func $add))  //export add function that can be used in javascript

2. How to share memory data

create memory in webassembly and export in to JS

  (memory 1) //1 means 1 page of memory, page has around 64kb
  (data (i32.const 0) "Hello World") //start from index 0 load the memory
  (memory $mem2)
  (export "mem" (memory 0)) //export te memory at index 0
  (export "mem2"(memory $mem2)

create memory in JS and import into webassembly

const memory = new WebAssembly.Memory({ initial: 1 }) //create 1 page of memory
const importMemory = {
  js: {
    mem: memory,

in webassembly

(memory (import "js" "mem") 1)