You can't - it's rubbish.
Look at the last bit:
else{day == "Monday");
{
document.write("Today is "+day);
}
What is that supposed to mean?
The brackets don't match, else doesn't have a condition, if the condition is intended as a statement it does nothing - but the document.write will always be executed regardless of the code above it.
It won't compile in any language I am aware of, and looks like you have grabbed random bits from the internet and chucked them together without thinking about what you are trying to achieve. If true, that is not a successful design strategy! :laugh: