The "with" keyword in Javascript

from: http://javascript.about.com/library/blwith.htm

The "with" keyword is used to specify an object to which all of the unreferenced properties and methods in a following block of code are to be applied.

for example:

Instead of coding

var x = document.body.scrollLeft;
document.write('text1');
document.write('text2');
document.write('text3');

you could use

with document {
var x = body.scrollLeft;
write('text1');
write('text2');
write('text3');
}

Of course using this construct results in code that may be somewhat shorter but it will also take a lot longer to run since each variable within the with block needs to be checked to see whether or not it is a property of the object that the with block references.

A more efficient coding that is almost as short is where you assign a much shorter name to reference the object and use that instead of the original object name. For example:

var d = document;
var x = d.body.scrollLeft;
d.write('text1');
d.write('text2');
d.write('text3');

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