CODEWITHSUNDEEP
javascript
Simon-Okp
Simon-Okp

Reputation: 697

method pointer/ref in javascript

Here is an example of my current code :

var myObject = new Obj();

if(something)
    myObject.method1(arg1, arg2);
else
    myObject.method2(arg1, arg2);

and how I declared my obj :

function Obj() { }

Obj.prototype.method1 = function(a, b) { }
Obj.prototype.method2 = function(a, b) { }

Since i'm doing this kind of test a bunch of time, I was wondering if it was possible to do something like that : 

if(something)
    var method = method1;
else
    var method = method2;

myObject.method(arg1, arg2);

Upvotes: 2

Views: 59

Answers (3)

Adassko
Adassko

Reputation: 5343

you can just do:

var method = myObject.method1;

then call it like:

method.call(myObject);

but you can also bind method to an object:

var method = myObject.method1.bind(myObject);

then you can call it normally:

method();

and this inside will be myObject

you can replace bind with simple:

var method = function() { myObject.method1(); }

if you want to support older browsers

Upvotes: 0

Rahul Tripathi
Rahul Tripathi

Reputation: 172518

You use a function reference in a variable like this:-

var method;
if(something)
    var method = myObject.method1;
else
    var method = myObject.method2;

method.call(myObject, arg1, arg2);

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1074929

Yes, functions are first-class objects in JavaScript, so you can store function references in variables and then call the function via the variable. In your case, you need to do that in a special way to ensure that this is myObject within the call:

var method;
if(something)
    method = myObject.method1;
else
    method = myObject.method2;

method.call(myObject, arg1, arg2);

Note the use of call there at the end: That allows you to call a function and control what this is within the function call.

If the condition really is that short, you can do this:

var method = something ? myObject.method1 : myObject.method2;
method.call(myObject, arg1, arg2);

Or even:

var method = something ? "method1" : "method2";
myObject[method](arg1, arg2);

More to explore:

Upvotes: 2

Related Questions