quickjs-go

Go bindings to QuickJS: a fast, small, and embeddable ES2020 JavaScript interpreter.

Version Support

quickjs-go	QuickJS
v0.1.x	v2021-03-27
v0.2.x	v2023-12-09
v0.3.x	v2024-01-13
v0.4.x	v2024-02-14

Features

Evaluate script
Compile script into bytecode and Eval from bytecode
Operate JavaScript values and objects in Go
Bind Go function to JavaScript async/sync function
Simple exception throwing and catching

Guidelines

Free quickjs.Runtime and quickjs.Context once you are done using them.
Free quickjs.Value's returned by Eval() and EvalFile(). All other values do not need to be freed, as they get garbage-collected.
Use ctx.Loop() wait for promise/job result after you using promise/job
You may access the stacktrace of an error returned by Eval() or EvalFile() by casting it to a *quickjs.Error.
Make new copies of arguments should you want to return them in functions you created.

Usage

import "github.com/buke/quickjs-go"

Run a script

package main

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

func main() {
    // Create a new runtime
    rt := quickjs.NewRuntime()
    defer rt.Close()

    // Create a new context
    ctx := rt.NewContext()
    defer ctx.Close()

    ret, err := ctx.Eval("'Hello ' + 'QuickJS!'")
    if err != nil {
        println(err.Error())
    }
    fmt.Println(ret.String())
}

Get/Set Javascript Object

package main

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

func main() {
    // Create a new runtime
    rt := quickjs.NewRuntime()
    defer rt.Close()

    // Create a new context
    ctx := rt.NewContext()
    defer ctx.Close()

    test := ctx.Object()
    test.Set("A", ctx.String("String A"))
    test.Set("B", ctx.String("String B"))
    test.Set("C", ctx.String("String C"))
    ctx.Globals().Set("test", test)

    ret, _ := ctx.Eval(`Object.keys(test).map(key => test[key]).join(" ")`)
    defer ret.Free()
    fmt.Println(ret.String())
}

Bind Go Funtion to Javascript async/sync function

package main
import "github.com/buke/quickjs-go"

func main() {
    // Create a new runtime
	rt := quickjs.NewRuntime()
	defer rt.Close()

	// Create a new context
	ctx := rt.NewContext()
	defer ctx.Close()

	// Create a new object
	test := ctx.Object()
	defer test.Free()
	// bind properties to the object
	test.Set("A", test.Context().String("String A"))
	test.Set("B", ctx.Int32(0))
	test.Set("C", ctx.Bool(false))
	// bind go function to js object
	test.Set("hello", ctx.Function(func(ctx *quickjs.Context, this quickjs.Value, args []quickjs.Value) quickjs.Value {
		return ctx.String("Hello " + args[0].String())
	}))

	// bind "test" object to global object
	ctx.Globals().Set("test", test)

	// call js function by js
	js_ret, _ := ctx.Eval(`test.hello("Javascript!")`)
	fmt.Println(js_ret.String())

	// call js function by go
	go_ret := ctx.Globals().Get("test").Call("hello", ctx.String("Golang!"))
	fmt.Println(go_ret.String())

	//bind go function to Javascript async function
	ctx.Globals().Set("testAsync", ctx.AsyncFunction(func(ctx *quickjs.Context, this quickjs.Value, promise quickjs.Value, args []quickjs.Value) {
		promise.Call("resolve", ctx.String("Hello Async Function!"))
	}))

	ret, _ := ctx.Eval(`
			var ret;
			testAsync().then(v => ret = v)
		`)
	defer ret.Free()

	// wait for promise resolve
    ctx.Loop()

    //get promise result
	asyncRet, _ := ctx.Eval("ret")
	defer asyncRet.Free()

	fmt.Println(asyncRet.String())

	// Output:
	// Hello Javascript!
	// Hello Golang!
	// Hello Async Function!
}

Error Handling

package main

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

func main() {
    // Create a new runtime
    rt := quickjs.NewRuntime()
    defer rt.Close()

    // Create a new context
    ctx := rt.NewContext()
    defer ctx.Close()

    ctx.Globals().SetFunction("A", func(ctx *Context, this Value, args []Value) Value {
        // raise error
        return ctx.ThrowError(expected)
    })

    _, actual := ctx.Eval("A()")
    fmt.Println(actual.Error())
}

Bytecode Compiler

package main

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

func main() {
    // Create a new runtime
    rt := quickjs.NewRuntime()
    defer rt.Close()
    // Create a new context
    ctx := rt.NewContext()
    defer ctx.Close()

    jsStr := `
    function fib(n)
    {
        if (n <= 0)
            return 0;
        else if (n == 1)
            return 1;
        else
            return fib(n - 1) + fib(n - 2);
    }
    fib(10)
    `
    // Compile the script to bytecode
    buf, _ := ctx.Compile(jsStr)

    // Create a new runtime 
    rt2 := quickjs.NewRuntime()
    defer rt2.Close()

    // Create a new context
    ctx2 := rt2.NewContext()
    defer ctx2.Close()

    //Eval bytecode
    result, _ := ctx2.EvalBytecode(buf)
    fmt.Println(result.Int32())
}

Runtime Options: memory, stack, GC, ...

package main

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

func main() {
    // Create a new runtime
    rt := quickjs.NewRuntime()
    defer rt.Close()

    // set runtime options
    rt.SetMemoryLimit(256 * 1024) //256KB
    rt.SetMaxStackSize(65534)

    // Create a new context
    ctx := rt.NewContext()
    defer ctx.Close()

    result, err := ctx.Eval(`var array = []; while (true) { array.push(null) }`)
    defer result.Free()
}