Use string variable as object fields

Question

I need to choose a property to animate and then, do animation.

The code should be like a following:

var prop = "background-color";
switch( val )
{
   case 1: prop = "color";
   case 2: prop = "border-color";
   // ...
}
item.animate( {prop: "#00FF00"}, 1000 );

JavaScript complains about using "prop" variable.

When i just say

item.animate( {"color": "#00FF00"}, 1000 );

everything is fine.

I think, a constant is expected as object property declaration.

How can i determine it at runtime ?

Sean Patrick Floyd · Accepted Answer · 2010-11-02 09:15:38Z

5

These are equivalent:

// prop is a literal string here,
// not a variable
{prop: "#00FF00"}

and

{"prop": "#00FF00"}

you probably need to do something like this:

var obj = {};
obj[prop]="#0000ff";
item.animate( obj, 1000 );

answered Nov 2, 2010 at 9:15

Sean Patrick Floyd

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Comments

Tim Down · Accepted Answer · 2010-11-02 09:14:19Z

2

Yes, you're correct, JavaScript expects an identifier as the property name in an object literal. You'll have to create an object and assign the property using square bracket notation.

var opts = {};
opts[prop] = "#00FF00";
item.animate(opts, 1000);

answered Nov 2, 2010 at 9:14

Tim Down

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