JavaScript: Convert string to value of predefined variable

Question

I have a JavaScript object that looks like the following:

venue = function(map, dataSet) {
    // set some constants
    this.VENUE_ID = 0;
    this.VENUE_NAME = 1;
    this.VENUE_CITY = 2;

    this.filterBy = function(field, value) {
        ...
        var filterValue = 'parent.VENUE_' + field;
    }
}

Now, the problem is that I need the value of filterValue to contain the value of the constant on the parent object. Currently I have tried using the method shown above and then referencing the filterValue when trying to access the array item, but this simply returns undefined.

How do I convert the filterValue variable into the value of the constant it represents?

BYK · Accepted Answer · 2009-07-29 10:26:00Z

3

This has nothing to do with the variable scope.

var filterValue = this['VENUE_' + field];

would do.

answered Jul 29, 2009 at 10:26

BYK

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Comments

mwilcox · Accepted Answer · 2009-07-29 12:46:26Z

2

JavaScript has no concept of 'parent'. And I think you're confusing scope and context. If that method was written as var filterBy() you'd have to access it in a different 'scope'. But by using 'this' you kept in in the same object as it was written. So everything you wrote is in 'this' context.

answered Jul 29, 2009 at 12:46

mwilcox

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1 Comment

tombazza Over a year ago

Ah I see! Well thank you, I had no idea. I had been manually setting the parent to 'this' externally to each function up until this point. I think the reason was something to do with using functions as callbacks.

Gumbo · Accepted Answer · 2009-07-29 10:26:14Z

1

Try this:

var filterValue = this['VENUE_' + field];

answered Jul 29, 2009 at 10:26

Gumbo

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