Microsoft® JScript® with Statement 
Language Reference Version 1

Establishes the default object for a statement.
with (object)
statementThe with statement syntax has these parts:
Part Description object The new default object.
statement The statement for which object is the default object. Can be a compound statement.
The with statement is commonly used to shorten the amount of code that you have to write in certain situations. In the example that follows, notice the repeated use of Math:When you use the with statement, your code becomes shorter and easier to read:x = Math.cos(3 * Math.PI) + Math.sin(Math.LN10) y = Math.tan(14 * Math.E)with (Math) { x = cos(3 * PI) + sin (LN10) y = tan(14 * E) }