marlun78/intercept

Simple metaprogramming for methods

Intercept

Simple metaprogramming for methods.

The intercept-function enables input and output hooks that will run before and after the intercepted method. In the input-hook lets you control the input to the intercepted method and the output-hook the return value.

Simple Example

// Some object
var math = {
    // Original method
    add: function add(a, b) {
        return a + b;
    }
};

// Now we intercept this method to control its in- and outputs.
// A `release`-function is returned to release the intercepted method and
// revert it to its original state.
var release = intercept(math, 'add',
    // The first function controls the input
    function input(args) {
        console.log('in', args);
        return [5, 5]; // Important to return an array!
    },
    // The second function controls the output
    function output(value) {
        console.log('out', value);
        return 'Monkey'; // Important to return the value!
    }
);

// Now we call the method
math.add(1, 2);
//=> in [1, 2]
//=> out 10
//=> 'Monkey'

// If we release the method and call it again
release();
math.add(2, 3);
//=> 5

Arguments

host

Object - The object to which the method belongs

name

String - The name of the method to intercept

input (optional)

Function - A function to be called before the original implementation and lets you control the input to the method. If supplied, it MUST return an array of arguments to the original implementation!

output (optional)

Function - A function to be called after the original implementation and it lets you control the output of the method. If supplied, what ever it returns will be used as the return value of the method.

Returns

Function - A function to release the method and revert it to its original state.