CODEWITHSUNDEEP
javascript
Ximik
Ximik

Reputation: 2495

Specify function only for one instance

I am a newbie in JavaScript and so don't really understand its object model, but as I understood I have to do something like. 

function set_test(text) { this['test'] = text; };
a = {};
text = 'ok';
a.prototype.ok = set_test(text);
alert(a['test']); #Should be 'ok'
text = 'fail';
a.ok;
alert(a['test']); #Should be 'ok'

Can somebody say what's wrong here?

Upvotes: 0

Views: 143

Answers (3)

J. K.
J. K.

Reputation: 8368

I think the whole code is wrong.

You see, in JavaScript, functions are objects and you can pass them around as you wish. The execution context (this) depends on the way you invoke a function.

If you store a function in a property of an object and then invoke it by calling obj.fn(), the execution context is set to obj.

Also notice that you aren't supposed to invoke the function when assigning it as the object's property.

function set_test(text) { this['test'] = text; }

var a = {};
a.ok = set_test; // see, no invocation

a.ok('abc');
alert(a['test']); // alerts 'abc'

a.ok('def');
alert(a['test']); // alerts 'def'

Upvotes: 1

Chad
Chad

Reputation: 19609

Objects don't have a prototype by default, and a.prototype.ok = set_test(text); would make ok equal to the return value of set_test() which is undefined.

Try doing it this way instead:

function set_test(text) { this['test'] = text; };
var a = {
    ok: set_test
},
text = 'ok';

a.ok(text);
alert(a['test']); //Should be 'ok'

text = 'fail';
a.ok(text);
alert(a['test']); //Should be 'fail'

Upvotes: 1

Valter
Valter

Reputation: 89

I think in function set_test this['test'] will not work. beacause "this" is not "a". You should define method set_test under object a - then it will work.

I recomend you check Mootools docs - there is much better object model syntax. You can also check Mootools source to get more detail answer to you question and js object model

Upvotes: 0

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