Find a variable using jquery

Question

I have a number of javascript variables on my page:

var opts_???? = ...
var opts_???? = ...
var opts_???? = ...

The ???? is assigned a random number by the content management system, so I don't know the full name of the variable.

I'm looking for any undefined ones.

Is there a way in jQuery to loop through all variables that start with opts_ so that I can test them for being undefined?

The variables are all global, if that helps.

If not in jQuery, I'll settle for regular javascript.

Does the variable name correspond to a name, class, or id attribute of an html element on the page? — Brian Driscoll, Jun 07 '16 at 14:21

Alnitak · Accepted Answer · 2016-06-07T14:30:22.643

This is only possible if the variables have all been declared at global scope (and therefore also available as properties of the global window object).

Since yours are, you can use Object.keys(window) to obtain the names of all such properties, and then use either $.each or Array.prototype.forEach to test each of them in turn.

var opts = Object.keys(window).filter(function(n) {
    return n.substring(0, 5) === 'opts_';
});

var opts_undefined = opts.filter(function(n) {
    return window[n] === undefined;
});

[written as two calls for clarity over efficiency]

Stephan Muller · Answer 2 · 2016-06-07T14:30:46.710

6

If the variables are in the global scope (that is, not created within a function) they should also be available as properties on the window object. In other words, the variable opts_1234 can also be accessed as window.opts_1234 or window['opts_1234'].

The easiest way to grab all the variables would be:

var variables = Object.keys(window).filter(function(prop) {
    return prop.substring(0, 5) === 'opts_';
});

Now variables contains an array of names, like ['opts_1', 'opts_666']

You can also extend that filter to only include those variables that aren't undefined:

var variables = Object.keys(window).filter(function(prop) {
    return prop.substring(0, 5) === 'opts_' && window[prop] !== undefined;
});

edited Jun 07 '16 at 14:30

answered Jun 07 '16 at 14:23

Stephan Muller

27,018
16
85
126

`.indexOf` is (IMHO) the wrong function for this job. – Alnitak Jun 07 '16 at 14:25
I considered using a regex, but I'm not sure it would make a big difference. What do you suggest? – Stephan Muller Jun 07 '16 at 14:26
2

well, in my answer I've used `.substring()`, since I explicitly only want to test the first five characters. The problem with `.indexOf` is that it'll scan the entire string unnecessarily. – Alnitak Jun 07 '16 at 14:27
Good point, I'll update my answer – Stephan Muller Jun 07 '16 at 14:28

score 1 · Answer 3 · answered Jun 07 '16 at 14:26

1

var opts_1 = 'test';
var opts_2 = 'test1';
var opts_3 = 'test2';
var opts_4 = undefined;

var vars = Object.keys(window).filter(function(key){
   return (key.indexOf("opts_")!=-1 && window[key] == undefined) 
});
console.log(vars);

answered Jun 07 '16 at 14:26

Vladu Ionut

8,075
1
19
30

asif · Answer 4 · 2016-06-07T14:34:17.510

0

Use:

var marker='opts_';
var results=$('selector').find(marker);

Hope This will help you

edited Jun 07 '16 at 14:34

answered Jun 07 '16 at 14:26

asif

11
4

Find a variable using jquery

4 Answers4