javascript variable and value concatenation

Question

I have a list of variables:

subcatlist1 = 'aa';
subcatlist2 = 'bb';
subcatlist3 = 'cc';

What i would like to do, is insert the value of a given variable from the option options, into an element, but the 'number' of the variable (ie, 1, 2 or 3) is itself coming in as a variable, say itemNumber.

What I would like to do is: $(element).html(subcatlist+ itemNumber);

... Which would give the value of aa for itemNumber = 1

The error that I am getting is: ReferenceError: subcatlist is not defined - which make sense, because the variable subcatlist doesn't exist - only subcatlist1, subcatlist2, subcatlist3 exist.

Do how can i concatenate the subcatlist+ itemNumber to get a variable that i can use, as subcatlist1 etc?

Thanks

Sudharsan S · Accepted Answer · 2014-07-23 08:05:11Z

2

Use object instead of variable is better approach in your context,Because you concadenate with variable is wrong.

var subcatlist = {1:"aa",2:"bb",3:"cc"}

$(element).html(subcatlist[itemNumber]);

edited Jul 23, 2014 at 8:05

answered Jul 23, 2014 at 8:00

Sudharsan S

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giulp · Accepted Answer · 2021-09-08 16:39:49Z

Updated

The solution is to access the needed variable as a property of the containing object.

If defined in the global scope using var , in javascript the value is assigned as a property of the global object, and it can be accessed using the self explanatory keyword globalThis

In JavaScript, there's always a global object defined. In a web browser, when scripts create global variables defined with the var keyword, they're created as members of the global object. (In Node.js this is not the case.)

var subcatlist1 = 'aa';
var subcatlist2 = 'bb';
var subcatlist3 = 'cc';

var itemNumber = parseInt(Math.random() * 3) + 1

$('#test').html(globalThis['subcatlist' + itemNumber])

<script 
  src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<div id="test">

See also "Variable" variables in JavaScript

Original answer

~~If having a list of variables is mandatory you could use eval() like this:~~

~~$(element).html(eval("subcatlist"+ itemNumber));~~

eval can be harmful and should be avoided in most cases

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