JavaScript和扩展的第三方API

Question

I'm updating my knowledge about JavaScript and I stuck on one lesson task. I have API that is returning string...

API.workerName = function (worker) {
   return worker.firstName + ' ' + worker.lastName;
};

The task is to prefix returning string and not change API, but extend it. I also have to avoid copying & pasting code, because 3rd party code can change. I should re-use it instead. What I did is change this function after loading API...

API.workerName = function (worker) {
   return '(' + worker.position + ') ' + worker.firstName + ' ' + worker.lastName;
};

... but I think I did it wrong.

Answer 1

To extend the method, you should save the old definition and call it from your extension:

API.oldWorkerName = API.workerName;
API.workerName = function(worker) {
    return '(' + worker.position + ')' + API.oldWorkerName(worker);
};

Or maybe this is what your lesson is looking for:

API.workerPositionAndName = function(worker) {
    return '(' + worker.position + ')' + API.workerName(worker);
};

Answer 2

Another neat way to save the old definition and also make it unavailable to anybody else, would be to do something like this using IIFE to create a closure:

API.workerName = (function() {
    var old = API.workerName;     // this old version is only available inside your new function
    return function(worker) {
        return '(' + worker.position + ')' + old(worker);
    }
})();

Here's an example:

 API = { workerName: function (worker) { return worker.firstName + ' ' + worker.lastName; } }; API.workerName = (function () { var old = API.workerName; return function (worker) { return '(' + worker.position + ')' + old(worker); }; })(); alert(API.workerName({firstName: "Joe", lastName: "Blogs", position: "Lackey" }));