Simple function locking in javascript

lock.js

var lock;

lock = function (object, functionName, lockFunction) {
    'use strict';

    var old;

    if (object[functionName].locked) {
        return false;
    }
    old = object[functionName];
    object[functionName] = lockFunction;
    object[functionName].locked = true;

    return function () {
        object[functionName] = old;
    };
};

How to use it?