vert's Introduction

vert

Package vert provides WebAssembly interop between Go and JS values.

Install

GOOS=js GOARCH=wasm go get github.com/norunners/vert

Examples

Hello World!

Below is a trivial string value interop.

package main

import "github.com/norunners/vert"

func main() {
	v := vert.ValueOf("Hello World!")
	// Use v as a JS value.

	s := ""
	v.AssignTo(&s)
	// Use s as a Go value.
}

Structs & Objects

Go structs and JS objects interop seamlessly.

package main

import "github.com/norunners/vert"

type Data struct {
	Message string
}

func main() {
	v := vert.ValueOf(Data{
		Message: "Hello World!",
	})
	// e.g. {"Message": "Hello World!"}

	d := &Data{}
	v.AssignTo(d)
}

Tagged Struct Fields

Tagged struct fields allow defined JS field names.

package main

import "github.com/norunners/vert"

type Data struct {
	Message string `js:"msg"`
}

func main() {
	v := vert.ValueOf(Data{
		Message: "Hello World!",
	})
	// The defined JS tag names the field.
	// e.g. {"msg": "Hello World!"}

	d := &Data{}
	v.AssignTo(d)
}

Error Handling

AssignTo returns an error value.

package main

import "github.com/norunners/vert"

type Data struct {
	Message string
}

func main() {
	v := vert.ValueOf("Hello World!")

	d := &Data{}
	if err := v.AssignTo(d); err != nil {
		// Handle error.
	}
}

Why?

Package syscall/js, of the Go standard library, has limited interop support between Go and JS values.

The function js.ValueOf will not accept struct types. The result panics with ValueOf: invalid value.
The type js.Value. does not support an Interface or assignment method for non-basic Go values. However, the methods Bool, Int, Float and String support basic Go values.