edit javascript on the fly

I was curious how I might go about editing a variable on t开发者_开发知识库he fly, since whenever I try nothing happens. Take http://nyan.cat for example. I tried to edit the seconds variable, but nothing happened - why?

i used (in the JS console) seconds = 9001; RET and nothing happens....

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That's because in http://nyan.cat/ the seconds variable is being set by the script repeatedly, based on the startTime Date object. In the specific case of http://nyan.cat/, to 'hack' the time, change the startTime.

Example: to increase your seconds by 1234567 seconds:

startTime = new Date(((+startTime/1000)-1234567)*1000);

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What JS console are you using?In the firebug?

Here I tested it.

var seconds = 9001;

alert(seconds);