annotation WebExtension::JSCInstanceMethod
Overview
Alizarin allows us to create custom JavaScript classes using plain Crystal classes.
All we need to do is to register our classes using WebExtension.register_class macro.
Note that if we need to expose any method of our Crystal's class so we can call it in JavaScript later, we must annotate it with this annotation, JSCInstanceMethod.
The example bellow demonstrates how to create a custom JavaScript class which allow us to read content of given file on disk.
- extension.cr
require 'alizarin'
include WebExtension
class File #here we do not have to construct a new class from scratch, just extend existing one.
def initialize(params : [] of JSCObject | JSCFunction | JSCPrimative)
super(params.first.to_s)
end
@[JSCInstanceMethod]
def content(p)
self.seek(0)
self.gets_to_end
end
end
initialize_extension do
JSCContext.set_value "File", register_class(File)
end- index.js
var file_content = new File("./LICENSE").content();
console.log(file_content);