dynamically get properties using method in javascript OOP

Question

If I create a class SONG(), and define many properties, how can i create a method that will use an argument passed through and get that property?

function SONG(i) {

    /* properties */
    this.title      = results.title[i];
    this.artist     = results.artist[i];
    this.album      = results.album[i];
    this.info       = results.info[i];

    /* methods */
    this.getstuff = function(stuff){
        console.log(this.stuff); // doesn't work
    }
}

var song1 = new SONG(1);

song1.getstuff(title);  
// how can I have this dynamically 'get' the property passed through as an argument?

any help or advice is greatly appreciated!

That is because your inner `this.stuff` is referring to the annon function that it's inside of. — Ryan, Feb 06 '13 at 14:56
Note that `song1.getstuff(title);` tries to pass the **variable** `title` (which is not defined) to `getstuff`. — Felix Kling, Feb 06 '13 at 14:56
@ryan: Since the object does not have a property `stuff`, `this.stuff` is simply `undefined`. — Felix Kling, Feb 06 '13 at 14:58

score 1 · Answer 1 · answered Feb 06 '13 at 14:56

1

You can use square-bracket notation:

this[title]

will get the property with the name contained in the title variable.

answered Feb 06 '13 at 14:56

Levi Botelho

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Hey thanks for the reply, not sure where I would put this in. I have `this[title]` in the function – d-_-b Feb 06 '13 at 15:04
Where is your function code ? – Levi Botelho Feb 06 '13 at 15:04
nevermind, this worked! I think i was not passing the argument as a string. Thanks! – d-_-b Feb 06 '13 at 15:08

score 1 · Accepted Answer · answered Feb 06 '13 at 14:59

Maybe this is what you want: (JSFiddle)

function SONG(i) {
    /* properties */
    this.title      = "My Title";
    this.artist     = "My Artist";
    /* methods */
    this.getstuff = function(stuff){
        if (this.hasOwnProperty(stuff))
            return this[stuff];
        else
            return null;
    }
}

var song1 = new SONG(1);

console.log(song1.getstuff("title"));  
console.log(song1.getstuff("invalid"));

But notice here that we are passing in "title" as a string. Also, there needs to be a check within getstuff to validate that SONG indeed has the property that is being requested, hence the check for hasOwnProperty.

THANKS! I think i was not passing the argument as a string as you said. — d-_-b, Feb 06 '13 at 15:08

dynamically get properties using method in javascript OOP

2 Answers2