Question

How to shift between variable names in jQuery and change them?

//predefined variables
var s1='';
var d2='';
//trying to change variables by .attr() parameter but no luck
$('body').on('click','span', function() {
var $(this).parent().attr('data-scan')=$(this).attr('id');
});

HTML

<div data-scan="s1"><span id="banana">Banana</span><span id="apple">Apple</span></div>
<div data-scan="d2"><span id="orange">Orange</span><span id="apple">Apple</span></div>

How can I change specific variables? I do’t care about changing attr papameter, all I need is changing predefined global var parameters!

Answer 1

Firstly, your html for the data-scan attributes is wrong, you have no closing quotes.

Secondly, you can the data() jquery function to access data attributes.

Thirdly, you cannot set values by using the = operator.

You want something like this:

 $(this).parent().data('scan', $(this).attr('id'));

or, without the data() function:

 $(this).parent().attr('data-scan', $(this).attr('id'));

Here is a working example

---

To get the value you can do one of the following:

var dataScan = $(this).parent().data('scan');

or

var dataScan = $(this).parent().attr('data-scan');

---

Your exact requirements for setting a variable based on the data-scan value

Based on your comments and code, I think it has not been clear what you were trying to do. I think I have worked it out though and you want to use the data-scan value to determine which global variable should be set…

//predefined variables
var s1='';
var d2='';

$('body').on('click','span', function() {
    var variableType = $(this).parent().data('scan');
    var valueToSet = $(this).attr('id');
    if(variableType == "s1"){
       s1 = valueToSet;
    }
    else if(variableType == "d2"){
       d2 = valueToSet;
    }
});

Here is an example of what I think you are trying to do.

However, if you have lots of variables then it is not ideal to use so many if/else statements. So you could use the javascript eval() function.

var variableType = $(this).parent().data('scan');
var valueToSet = $(this).attr('id');

eval("" + variableType + " = '" + valueToSet + "';");

See here for an example

But be careful the your eval code is subjected to user injected values (not that javascript is safe from users anyway)