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Functions in AssemblyScript

Functions in AssemblyScript work just like in TypeScript. There are only two differences:

  • You need to provide types for parameters and returns
  • Closures are not supported yet. More on it later in the article

Writing a function

This example of a function is provided in the starter template of every AssemblyScript project.

function add(a: i32, b: i32): i32 {
return a + b

Calling functions in JavaScript

Functions need to be exported before you can use them in JavaScript

export function add(a: i32, b: i32): i32 {
return a + b

Once you build the code, import and use the function in JavaScript

import { add } from './build/release.js'
console.log(add(2, 1))


The following code structure would lead to erros, as we create different closures. A variable in the first scope could not be accessed in the wrapped scope.

function () {
return function b() {
function sumTimesTen(a: i32, b: i32): i32 {
const sum: i32 = a + b

return sum * 10