js中with（）的用法

with Statement

Establishes the default object for a statement.



with (object)

   statements



Arguments

object



The new default object.



statements



One or more statements for which object is the default object.



Remarks

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.



x = Math.cos(3 * Math.PI) + Math.sin(Math.LN10)

y = Math.tan(14 * Math.E)

When you use the with statement, your code becomes shorter and easier to read:



with (Math){

   x = cos(3 * PI) + sin (LN10)  

   y = tan(14 * E)

}

Requirements