正则表达式基本上就是为进行文本处理而构建的一种小型的子语言，用来进行字符串的匹配和替换。

Regular expressions are basically a small sub-language built for text processing, used to match and replace strings of characters.

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它带两个参数——替换文本节点和被替换的子元素。

This takes in two parameters — the replacement text node and the child element that it's replacing.

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