See what the variable is on a variable change with js? [duplicate]

Question

I have a variable I will call x and I want to see what the variable is when it changes.

Incomplete demo:

var x = 0; x = 1; whenxchanges = { if (x == 0){ alert(x); } else { alert(x); } }

Demo is just showing what I want to happen.

Thanks!

Please no Jquery

There is no event "simple" solution when a variable changes. — epascarello
– epascarello, Commented Dec 17, 2015 at 0:59
Well they are not the answers I want. I want a very simple version like in the demo — arodebaugh
– arodebaugh, Commented Dec 17, 2015 at 1:00
This might be what you want. But, there is no standard Event to test for variable changes. Usually you test for variable changes on a specific JavaScript Event. — StackSlave
– StackSlave, Commented Dec 17, 2015 at 1:18
Read the warning at the top of the page first, though. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Alberto Rivera
– Alberto Rivera, Commented Dec 17, 2015 at 1:51

Déjà vu · Accepted Answer · 2015-12-17 08:48:59Z

In a browser like Chrome or Firefox (firebug) you could run the program step by step, inspect the value, etc...

Besides, you cannot force Javascript to trigger an event when x changes.

However you could make a function (setx), having x global, or having setx a nested function within a function where x is defined:

function setx(v) { alert("x changes!"); x = v; }

Then instead of doing

x = 7;

you do

setx(7);

and the alert is triggered. Replace all x assignments with a call to setx and you'll be notified whenever x changes, ie whenever setx is called.

This is of course basic cross-browser JS.

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