How are variables injected into JavaScript in HTML?

Question

I realised that I don't know how variables are injected into JavaScript in HTML. I would like to test overriding a clickTag variable which is simply a var in the main body of a JavaScript ( a default value ), but to override it with the injected variable.

Something like this >

somewhere.com/index.html?{"clickTag":"http://www.something.com"}

What's the best way to do that ? Pretty basic, but I've been used to having the DoubleClick Enabler handling that for me and I have not thought about how the data actually gets in, and how I could test it.

( for a basic php file, passing variables the simplest way, it would be work.php?play=good&balance=true etc but I'm not finding a question here for what I have asked )

Please also correct my terminology if it is bad or misleading. Thanks.

See http://stackoverflow.com/questions/901115/how-can-i-get-query-string-values-in-javascript — JJJ, Feb 24 '16 at 13:45
Are you asking: How do I a pass a value to a HTML page and display that value using JavaScript? — Martin, Feb 24 '16 at 13:46
Do you mean, you want to read the value of a querystring parameter from Javascript so you can update the page with it? — CompanyDroneFromSector7G, Feb 24 '16 at 13:50

score 1 · Accepted Answer · answered Feb 24 '16 at 13:46

Variables aren't injected into JavaScript.

A JavaScript program defines variables. It might get values to assign to them by accessing APIs (such as location in a web browser which would give you details of the URL of the page).

If you want to override the value of a variable in an existing program then you would need to change the source code of that program to write a new value to that variable between the point where it would normally be assigned and the point where it gets read back and used.

How are variables injected into JavaScript in HTML?

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