Javascript convert String to Object property

Question

i want to build my own PROP function just like what Jquery does, but in pure Java script.

this is my code :

<input id="submitButton" type="submit" value="LOGIN">

function prop(el, dom, boolean) {

    var convert = eval(dom);
    el.convert = boolean;
    console.log(convert);
}

var x = document.getElementById("submitButton");

prop(x, "disabled", true);

How to convert string into object property? I heard that eval will be useful? But why did i got the below error?

ReferenceError: disabled is not defined

what's wrong with my code?

use - el[dom], or el.setAttribute(dom,value) to manipulate properties of an el. — BatScream
– BatScream, Commented Dec 22, 2015 at 6:26
wow BatScream, your method works perfect! thank you so much!!!! you are A W E S O M E, anyway, i wonder what kind person that give me down votes for this questions lol — Ching Ching
– Ching Ching, Commented Dec 22, 2015 at 6:34
@BatScream - Why are the things you say in this comment (which holds the best answer) nowhere to be found in your actual answer? — Jimbo Jonny
– Jimbo Jonny, Commented Dec 22, 2015 at 6:49
@JimboJonny - have included it now. I thought the link and the comments would have sufficed. Thanks for pointing it out. — BatScream
– BatScream, Commented Dec 22, 2015 at 6:53

BatScream · Accepted Answer · 2015-12-22 06:52:31Z

3

You should not use eval() to convert property names into properties. Use Property accessors.

e.g., el[dom] or el.dom.

If the Object is an HTML element, you could use the setAttribute and getAttribute methods that are available.

when you pass in a string as argument to eval, it tries to represent the string as java script code.

Here, you have passed in a string disabled.

It gets represented as:

disabled;

The interpreter now tries to locate a variable named disabled. Since disabled is not a variable we have defined in the context, it throws the error: ReferenceError: disabled is not defined.

To validate this, try defining a variable and then invoking the eval() function on it.

var disabled = 10;
console.log(eval("disabled"));

prints: #10

edited Dec 22, 2015 at 6:52

answered Dec 22, 2015 at 6:42

BatScream

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Comments

Aiman Al-Eryani · Accepted Answer · 2015-12-22 06:26:23Z

0

It's because you're trying to evaluate what "disabled" alone is to. eval("document.getElementById('submitButton').disabled") would work.

answered Dec 22, 2015 at 6:26

Aiman Al-Eryani

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1 Comment

Ching Ching Over a year ago

This one also working! thanks Aiman Al-Eryani. you're the best!!

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