Typically, JavaScript code runs either on Node.js or in the browser. Any code that runs on Node.js should have access to what is known as Node.js global objects (https://nodejs.org/api/globals.html). If your code ends up running on a Node.js environment, GopherJS gives you access to the global objects using the js.Global variable, which returns a *js.Object that hosts your global variables. You can then access a specific object using a method called Get, then call the object methods using a method called Call. Let's see an example to better explain this paragraph.  

Run the following code:

package main

import (
  "github.com/gopherjs/gopherjs/js"
)

func main() {
  //the console variable is of type *js.Object
  console := js.Global.Get("console")
  /*
    the *js.Object support a method called Call which     can access the methods of console.
  */
  console.Call("log", "Hello world!!")
}

This will be the equivalent of writing a piece of Node.js JavaScript code that looks like this:

console.log("Hello World!!");

The js.Global object opens up very interesting possibilities, as it allows you to access Node.js modules and use them in your Go code. For example, let's assume we imported a Node.js module called prettyjson to our node project, and we would like to use it in our Go code. prettyjson is a real package, it has a method called render(), which converts objects to beautiful-looking JSON. This is shown in the following code:

package main

import (
  "fmt"

  "github.com/gopherjs/gopherjs/js"
)

func main() {
  //Some data type
  type MyType struct {
    Name string
    Projects []string
  }
  //A value from our data type
  value := MyType{Name: "mina", Projects: []string{"GopherJS", "ReactJS"}}
  /*
    Call the prettyjson module, this is equivalent to the following code in JavaScript:
        var prettyjson = require("prettyjson");
 */
  prettyjson := js.Global.Call("require", "prettyjson")

  // The line below is equivalent to 'prettyjson.render(value);' in JavaScript
  result := prettyjson.Call("render", value)
  /*
    Do something with result
    */
}

As mentioned, JavaScript code can also run on a browser. The globals available to the browser are different. For example, the following piece of code will run fine on a browser, but won't be happy if you try to run it with Node.js:

package main

import (
  "github.com/gopherjs/gopherjs/js"
)

func main() {
  document := js.Global.Get("document")
  document.Call("write", "Hello world!!")
}

That is because "document" is a global object available for almost all browsers.

In the next section, we will take a look at the GopherJS commands.