go-quickjs, make quickjs be embedded easily

QuickJS is a small and embeddable Javascript engine written by Fabrice Bellard.

go-quickjs is a package wrapping quickjs and making it a pragmatic embeddable language. With some helper functions provided by go-quickjs, calling Golang functions from Javascript, or calling Javascript functions from Golang are both very simple. So, with the help of go-quickjs, quickjs can be embedded in Golang application easily.

Install

The package is fully go-getable, So, just type

go get github.com/rosbit/go-quickjs

to install.

Usage

1. Evaluates expressions

package main

import (
  "github.com/rosbit/go-quickjs"
  "fmt"
)

func main() {
  ctx, err := quickjs.NewContext()
  if err != nil {
    fmt.Printf("%v\n", err)
    return
  }

  res, _ := ctx.Eval("a + b", map[string]interface{}{
     "a": 10,
     "b": 1,
  })
  fmt.Println("result is:", res)
}

2. Go calls Javascript function

Suppose there's a Javascript file named a.js like this:

function add(a, b) {
    return a+b
}

one can call the Javascript function add() in Go code like the following:

package main

import (
  "github.com/rosbit/go-quickjs"
  "fmt"
)

var add func(int, int)int

func main() {
  ctx, err := quickjs.NewContext()
  if err != nil {
     fmt.Printf("%v\n", err)
     return
  }

  if _, err = ctx.EvalFile("a.js", nil); err != nil {
     fmt.Printf("%v\n", err)
     return
  }

  // method 1: bind JS function with a golang var
  if err = ctx.BindFunc("add", &add); err != nil {
     fmt.Printf("%v\n", err)
     return
  }
  res := add(1, 2)

  // method 2: call JS function using CallFunc
  // res, err := ctx.CallFunc("add", 1, 2)
  // if err != nil {
  //   fmt.Printf("%v\n", err)
  //   return
  // }

  fmt.Println("result is:", res)
}

3. Javascript calls Go function

Javascript calling Go function is also easy. In the Go code, make a Golang function as Javascript global function by calling EvalFile by registering. There's the example:

package main

import (
    "github.com/rosbit/go-quickjs"
    "fmt"
)

// function to be called by Javascript
func adder(a1 float64, a2 float64) float64 {
    return a1 + a2
}

func main() {
  ctx, err := quickjs.NewContext()
  if err != nil {
      fmt.Printf("%v\n", err)
      return
  }

  if _, err = ctx.EvalFile("b.js", map[string]interface{}{
      "adder": adder,  // b.js containing code calling "adder"
  }); err != nil {
      fmt.Printf("%v\n", err)
  }
}

In Javascript code, one can call the registered function directly. There's the example b.js.

r = adder(1, 100)   // the function "adder" is implemented in Go
console.log(r)

Inspecting Go values with console.log

Go values passed to JS (maps, structs, pointers) are handed over with all fields at any nesting depth, and struct methods are callable as JS functions. console.log renders them so they can be inspected directly: fields are listed and methods show up as [Function: Name] instead of undefined.

console.log(me)   // me is a *Person set from Go
// {Greet: [Function: Greet], age: 18, greet: [Function: Greet], name: 绿兵, ...}
me.greet("hi")    // methods are called on the original Go value

Status

The package is not fully tested, so be careful.

Contribution

Pull requests are welcome! Also, if you want to discuss something send a pull request with proposal and changes. Convention: fork the repository and make changes on your fork in a feature branch.