Define-function NPM

About

quick.js based sandbox

npm install define-function

works in any WebAssembly environment

node
browser
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Usage

define a function dynamically with javascript source code

const def = require('define-function')
const f = await def(`
    return 'hello';
`)
f() // 'hello'

function can have argument

const def = require('define-function')
const f = await def(`
    const [hello, world] = arguments;
    return hello + ' ' + world;
`)
f('hello', 'world') // 'hello world'

argument can be function

const def = require('define-function')
const f = await def(`
    const [print] = arguments;
    print('hello')
`)
f((msg) => {
    console.log(msg)
}) // 'hello'

argument can be async function

const def = require('define-function')
const f = await def(`
    const [print, sleep] = arguments;
    (async() => {
        print('hello')
        await sleep(1000);
        print('world')
    })();
`)
f(
    msg => console.log(msg),
    milliseconds => new Promise(resolve => setTimeout(resolve, milliseconds))
) 
// hello
// world

can return promise back to host

const def = require('define-function')
const f = await def(`
    const [print, sleep] = arguments;
    return (async() => {
        print('hello')
        await sleep(1000);
        print('world')
    })();
`)
await f(
    msg => console.log(msg),
    milliseconds => new Promise(resolve => setTimeout(resolve, milliseconds))
)
console.log('done')
// hello
// world
// done

share context between multiple invocations

const { context } = require('define-function')
const ctx = context()
const f = await ctx.def(`
    global.counter = (global.counter || 0)+1;
    return counter; // counter can be referenced globally
`)
f() // 1
f() // 2
f() // 3
ctx.dispose()

inject value and callbacks into global

const { context } = require('define-function')
const ctx = context({ global: { 
    console,
    anwerOfEverything() {
        return 42;
    }
} }) // inject console and anwerOfEverything to global
const f = await ctx.def(`
    console.log(anwerOfEverything());
`)
f() // 42
ctx.dispose();

import and export es module

const { context } = require('define-function')
const ctx = context({ 
    loadModuleContent(moduleName) {
        if (moduleName !== 'xxx') {
            throw new Error('expect xxx');
        }
        return `export function sayHello() { return 'hello' }`
    }
});
const { hello } = await ctx.load(`
    import { sayHello } from 'xxx';
    export const hello = sayHello();
`)
console.log(hello) // hello
ctx.dispose();

Limit

function argument does not support Set/Map/Class or anything that can not survive JSON.parse(JSON.stringify), except the argument is a function
function return value does not support Set/Map/Class or anything that can not survive JSON.parse(JSON.stringify), except promise object
JSON.stringify and JSON.parse takes time, so the arguments and return value should be as small as possible for best performance