node-monkeypatch

Slightly easier monkeypatching.

Installation

npm install monkeypatch

Usage

monkeypatch(target : Object, method : String, handler : Function) : Function

Monkeypatching a method/function on a target object replaces the method with a newly supplied handler function which will get called instead of the original.

The original method will be returned by monkeypatch(), and will also be passed as the first argument to the new handler function. See examples.

Examples

Patching a function

var monkeypatch = require('monkeypatch');

// Monkeypatch Date.now()
monkeypatch(Date, 'now', function(original) {
  // Round to 15-minute interval.
  var ts = original();
  return ts - (ts % 900000);
});

var timestamp = Date.now(); // returns a rounded timestamp
...

Patching an instance method

var monkeypatch = require('monkeypatch');

// Monkeypatch Date#getTime()
monkeypatch(Date.prototype, 'getTime', function(original) {
  // Round to 15-minute interval.
  var ts = original();
  return ts - (ts % 900000);
});

var date      = new Date();
var timestamp = date.getTime(); // returns a rounded timestamp
...

Argument handling

var monkeypatch = require('monkeypatch');

// Monkeypatch Date#setTime()
monkeypatch(Date.prototype, 'setTime', function(original, ts) {
  // Round to 15-minute interval.
  ts = ts - (ts % 900000);
  // Call the original.
  return original(ts);
});

var date = new Date();
date.setTime(date.getTime()); // set to a rounded timestamp
...

Unpatching

var monkeypatch = require('monkeypatch');

// Monkeypatch Date.now()
monkeypatch(Date, 'now', function() { return 143942400000; });

console.log(Date.now()); // logs 143942400000

Date.now.unpatch();

console.log(Date.now()); // logs current time