jsbuiltin - Built-in JavaScript functions for GopherJS

JavaScript has a small number of built-in
functions
to handle some common day-to-day tasks. This package providers wrappers around
some of these functions for use in GopherJS.

It is worth noting that in many cases, using Go’s equivalent functionality
(such as that found in the net/url package)
may be preferable to using this package, and will be a necessity any time you
wish to share functionality between front-end and back-end code.

What is supported?

Not all JavaScript built-in functions make sense or are useful in a Go
environment. The table below shows each of the JavaScript built-in functions,
and its current state in this package.

Notes on unmplemented functions

• eval(): Is there ever a need to eval JS code from within Go?
• Number(): This requires handling a bunch of corner cases which don’t
  normally exist in a strictly typed language such as Go. It seems that anyone
  with a legitimate need for this function probably needs to write their own
  wrapper to handle the cases that matter to them.
• parseInt() and parseFloat(): These could be added, but doing so
  will require answering some questions about the interfce. JavaScript has
  effectively two relevant data types (int and float) where Go has has 12.
  Deciding how to map JS’s parseInt() to Go’s (u?)int(8|16|32|64) types,
  and JS’s parseFloat() Go’s float(32|64) or complex(64|128) needs to
  be considered, as well as how to handle error cases (Go doesn’t have a NaN
  type, so any NaN result probably needs to be converted to a proper Go
  error). If this matters to you, comments and/or PRs are welcome.

Installation and Usage

Get or update this package and dependencies with:

go get -u -d -tags=js github.com/gopherjs/jsbuiltin

Basic usage example

This is a modified version of the Pet example in the main GopherJS documentation,
to accept and return URI-encoded pet names using the jsbuiltin package.

package main
import (
    "github.com/gopherjs/gopherjs/js"
    "github.com/gopherjs/jsbuiltin"
)
func main() {
    js.Global.Set("pet", map[string]interface{}{
        "New": New,
    })
}
type Pet struct {
    name string
}
func New(name string) *js.Object {
    return js.MakeWrapper(&Pet{name})
}
func (p *Pet) Name() string {
    return jsbuiltin.EncodeURIComponent(p.name)
}
func (p *Pet) SetName(uriComponent string) error {
    name, err := jsbuiltin.DecodeURIComponent(uriComponent)
    if err != nil {
        // Malformed UTF8 in uriComponent
        return err
    }
    p.name = name
    return nil
}