Create GUI button in Unity using Javascript

Make a Scene, I called it Menu.

Create a JavaScript file, I named it MenuGUI.

Create a button. Rect makes rectangular at 0,0 two dimensional coordinates. Rectangular size is 200 pixels wide and 100 in height. OnGUI function gets iterated at every frame.

Source code viewer
function OnGUI() {
	GUI.Button(Rect(0,0,200,100), 'Button');
}
Programming Language: Javascript

Create an empty object form GameObject -> Create Empty or simply Ctrl+Shift+N. Attach the script to the empty object.

Make the button do something.

Source code viewer
function OnGUI() {
	if(GUI.Button(Rect(0,0,200,100), 'Button')) {
		// Code goes here...
	}
}
Programming Language: Javascript