How to pass a parameter to a function of an object in Javascript?

Question

I apologize, if this is a dublicate, but I can't find the answer I am looking for, although my problem seems to be easy.

This is what I have:

function myMain (myParam) {

    var myObj = {

        myVal1 : 'demo',
        myFunc : function (myParam) {
            console.log (myParam);
        }
    };

    runDemo(myObj);

}

My problem is that I want the console.log to write myParam of myMain, but it is undefined - why?

How can I call myMain('works') so that console writes works?

FYI: runDemo has too be called with this single Object and with myFunc as one of the objects values - no way around that. I am grateful for any help, thanks.

kzh · Accepted Answer · 2013-09-30 13:10:10Z

1

Make myFunc not take a parameter like so:

function myMain (myParam) {

    var myObj = {

        myVal1 : 'demo',
        myFunc : function () {
            console.log (myParam);
        }
    };

    runDemo(myObj);

}

In this case myFunc retains the value of the variable myParam. This is called a closure.

answered Sep 30, 2013 at 13:10

kzh

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2 Comments

Jook Over a year ago

nice, this works - I still do not quite get why, but it does ... thanks for the super fast answer! I will look up 'closure', but feel free to explain further ;)

kzh Over a year ago

It is similar to this: var a = 'foo'; function bar(){alert(a);}

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