Object prototype throws error even if object was not created in JS

Question

Help me grasp this please. I want to create object, which property "visible" and method "hi", but getting error on line 2:

TypeError: Cannot set property 'visible' of undefined

in:

var NewFilter = {};
NewFilter.prototype.visible = false;
NewFilter.hi = function () { console.info("hi"); }

OK I know that I have to actually create that object, but why the hell it's property throwing error when it should eventually do upon object creation?

Object instances do not have a `.prototype` property, the constructor function that created the instance does. What prototype is and what it can be used for is explained here: http://stackoverflow.com/a/16063478/1641941 — HMR, Apr 30 '14 at 08:59

score 1 · Accepted Answer · edited May 23 '17 at 10:32

1

Empty objects don't have a prototype property, so you can't set a property on it's (nonexistent) prototype.

Just set it on the object itself, instead:

var NewFilter = {};
NewFilter.visible = false;
NewFilter.hi = function () { console.info("hi"); }

If you want to learn more about JavaScript prototypes, I'd suggest looking for a few tutorials / sites.

edited May 23 '17 at 10:32

Community

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answered Apr 30 '14 at 07:30

Cerbrus

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@sebcap26: Oh, indeed. Copied that from the question, fixed both :-) I believe the privileges on "small" edits come with [2k rep](http://stackoverflow.com/help/privileges) – Cerbrus Apr 30 '14 at 07:36

Object prototype throws error even if object was not created in JS

1 Answers1