In writing an assignment statement, for example, you can declare variables of any type, use any identifier to the left of the equal sign, and supply any expression on the right.

例如你要写一句赋值语句，你可以声明任何类型的变量，在等号的左边使用任何标识符，然后在右边给出任何的表达式。

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This means that local variables actually move to an identifier depth of two during execution of the with, imposing a performance penalty.

这就意味着在执行with的过程中，实际上的局部变量都被移到作用域链上的第二个位置，这会带来性能上的损失。

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