This module allows you to create an ES6 class that is callable as a function. The invocation is sent to one of the object's normal prototype methods.
npm install callable-instance
In the following example, we will create an ExampleClass class. The instances have all of the normal properties and methods, but are actually functions as well.
import CallableInstance from "callable-instance";
// If you aren't using ES modules, you can use require:
// var CallableInstance = require("callable-instance");
class ExampleClass extends CallableInstance {
constructor() {
// CallableInstance accepts the name of the property to use as the callable
// method.
super("instanceMethod");
}
instanceMethod() {
console.log("instanceMethod called!");
}
}
var test = new ExampleClass();
// Invoke the method normally
test.instanceMethod();
// Call the instance itself, redirects to instanceMethod
test();
// The instance is actually a closure bound to itself and can be used like a
// normal function.
test.apply(null, [1, 2, 3]);TypeScript is also supported. CallableInstance is generic, accepting a tuple of arguments and a return type.
import CallableInstance from "callable-instance";
class ExampleClass extends CallableInstance<[number], string> {
constructor() {
super("instanceMethod");
}
instanceMethod(input: number): string {
return `${input}`;
}
}Note that the types specified may differ from the argument and return value types of the target method; this is an error due to a limitation of TypeScript.
All instances of CallableMethod are also an instances of Function, and have all of Function's properties.
Libraries that accept functions will expect that they behave as Function objects do. For example, if you alter the semantics of the call or apply methods, library code may fail to work with your callable instance. In these cases, you can simply bind the instance method to the callable instance and pass that instead (e.g. test.instanceMethod.bind(test)).
This can also cause problems if your derived class wants to have a name or length property, which are built-in properties and not configurable by default. You can have your class disable the built-in descriptors of these properties to make them available for your use.
var test = new ExampleClass();
test.name = "hello!";
console.log(test.name); // Will print 'instanceMethod'
class NameableClass extends CallableInstance {
constructor() {
super("instanceMethod");
Object.defineProperty(this, "name", {
value: void 0,
enumerable: true,
writeable: true,
configurable: true,
});
}
instanceMethod() {
console.log(this.name);
}
}
test = new NameableClass();
test.name = "hello!";
console.log(test.name); // Will print 'hello!'- Fork it!
- Create your feature branch:
git checkout -b my-new-feature - Commit your changes:
git commit -am 'Add some feature' - Push to the branch:
git push origin my-new-feature - Submit a pull request :D
Information for the implementation came from this StackOverflow answer.
Distributed under the MIT license.