reversevar.js

// Set multiple vars / obj props to the same value
el.style.width = x;
newWidth = x;
eventData.width = x;

// Set x as the value to these vars / obj props
x => (el.style.width, newWidth, eventData.width);

You mean like this?

el.style.width = newWidth = eventData.width = x;

LOL @techwraith

I thought JavaScript had a kind of multiple-assignment on the left-hand side, but maybe I was thinking of Ruby:
a, b, c = [1,2,3]
CoffeeScript has that destructuring assignment, in the form of:
[a, b, c] = [1,2,3]

I guess I was thinking, (with the addition of a repeat utility method), you could something like
el.style.width, newWidth, eventData.width = repeat(x, 3)
Where repeat just makes an array by repeating x n times.

What @techwraith said