Script Engine

Introduction

The script engine has two versions: js1.0 and js2.0. The script engine can be switched through the system parameter bingo.script.use.js2.0 . The differences between the script engines of the two versions are as follows:

Language feature support

Feature	js1.0	js2.0	Description
Support for ES standards	ES5.1, partial support for ES6+	ES2022
Module support	commonjs	es module/commonjs	switch module mode by bingo.js2.script.module system parameter.
Asynchronous Support (Promise/async/await)	N	Y
setTimeout,clearTimeout	N	Y
ES6 class support	Y	Y
Proxy	Y	Y
Symbol	Y	Y
Map, Set, WeakMap, WeakSet	Y	Y
Typed Arrays	Y	Y
for-of	Y	Y
Reflect	Y	Y
Block-scoped declarations (let and const)	Y	Y
Optional catch binding	Y	Y
Destructuring assignments	Y	Y
Default function parameters	Y	Y
Spread and rest properties	Y	Y
Arrow functions	Y	Y
Template literals	Y	Y
Optional chaining	Y	Y
** Operator	Y	Y
Nullish Coalescing Operator	Y	Y
generators	Y	Y
String.prototype.replaceAll	Y	Y

both js1.0 and js2.0 are not compatible with the'npm' ecosystem.

Performance Differences

The performance of js2.0 is much better than that of js1.0. In most scenarios, the performance is improved by 100% to 1000%. For example, JSON.parse is improved by 800%, and JSON.stringify is improved by 500%.

New APIs in JS 2.0

Because js2.0 supports asynchronization, some asynchronization api are added:

• setTimeout
• clearTimeout
• db.sql.executeAsync

import * as db from 'db';

function bad() {
    let p = db.sql().executeAsync("select * from m__wasm__cst limit 1", { dynamic: false });
    p.then((value) => {
        console.log(value);
    }).catch((reason) => {
        console.log("execption = ", reason);
    });
}

function ok() {
    let p = db.sql().executeAsync("select * from m__wasm__cst limit 1", { dynamic: true });
    p.then((value) => {
        console.log("affected rows = ", value.AffectedRows);
    }).catch((reason) => {
        console.log("execption = ", reason);
    });
}

console.log("hello 1");
setTimeout(ok, "1000");
console.log("hello 2");
setTimeout(bad, "100");
console.log("hello 3");

output:

0703 15:27:00.626|debug|vm[1]>>> hello 1 (m__obs:18)
0703 15:27:00.626|debug|vm[1]>>> hello 2 (m__obs:20)
0703 15:27:00.626|debug|vm[1]>>> hello 3 (m__obs:22)
0703 15:27:01.631|debug|vm[1]>>> affected rows =  1 (m__obs:13)
0703 15:27:01.631|debug|vm[1]>>> execption =  Error 
{
    message: "object m__wasm__cst is used but not decorated with @useObject, please decorate it first."
} (m__obs:7)

• http.client.requestAsync

import * as http from 'http';
import * as context from 'context';

const option: http.ClientOption = {
    baseUrl: context.getHost() + "/u-route/baas/"
}
const headers = {
    "access-token": context.getToken(),
    "content-type": "application/json",
};

const client = http.newClient(option);
let p = client.requestAsync(http.Method.GET, "script/v1.0/declaration", { headers: headers });

p.then((resp) => {
    console.log(`resp length is `, len(resp.body.result));
}).catch((reason) => {
    console.log(`error is `, reason);
});

console.log("hello, here");

output：

0712 16:46:57.832|debug|vm[68]>>> hello, here (m__httpdemo:19)
0712 16:46:57.832|debug|vm[68]>>> resp length is  2 (m__httpdemo:15)

dynamicly import module

commonjs uses the require function, and esmoudle uses the import function.

commonjs:

const res = require('./m__util');
res.sayHello('common js dynamic import');

esmodule:

import('./m__util').then((res) => {
    res.sayHello("es module dynamic import");
});

Compatibility Differences

Some AppCube APIs are different:

The Exponent method of the Decimal type has different results in some scenarios.

import * as decimal from'decimal';

let d1 = decimal.newFromString('- 123.4567');
let d2 = decimal.newFromString('- 321.231');
let avg = decimal.avg(d1, d2);
console.log("avg:", avg);
console.log("avg exponent:", avg.Exponent());

js1.0 Output Result

617 19:38:03.685|debug|vm[12]>>> avg: -222.34385 (m__avgdecimal.ts:6:12(36))
0617 19:38:03.685|debug|vm[12]>>> avg exponent: -16 (m__avgdecimal.ts:7:12(44))

The output of js2.0 is as follows:

0617 19:35:29.125|debug|vm[11]>>> avg: -222.34385 (m__avgdecimal:5)
0617 19:35:29.125|debug|vm[11]>>> avg exponent: -5 (m__avgdecimal:6)

From the output, the js2.0 output is more in line with our intuition.