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Tham khảo tài liệu 'professional information technology-programming book part 106', công nghệ thông tin, kỹ thuật lập trình phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Init var windowName spellWindow var spellCheckURL spell.cfm formname comment fieldname field. name Done return false SCRIPT A s . matches the start of a string followed by any whitespace followed by used to define JavaScript comments followed by any text and then an end of string. But that pattern would match only the first comment and only if it were the only text in the page . The m modifier in m A s . forces the pattern to treat line breaks as string separators and so all comments were matched. Caution m is not supported by many regular expression implementations. Note Some regular expression implementations also support the use of A to mark the start of a string and Z to mark the end of a string. If supported these metacharacters function much like A and respectively but unlike A and they are not modified by m and will therefore not operate in multiline mode. Summary Regular expressions can match any blocks of text or text at specific locations within a string. b is used to specify a word boundary and B does the exact opposite . A and mark string boundaries start of string and end of string respectively although when used with the m modifier A and will also match strings that start or end at a line break. Lesson 7. Using Subexpressions Metacharacters and character matching provide the basic power behind regular expressions as has been demonstrated in the lessons thus far. In this lesson you ll learn how to group expressions together using subexpressions. Understanding Subexpressions Matching multiple occurrences of a character was introduced in Lesson 5 Repeating Matches. As discussed in that lesson d matches one or more digits and https matches http or https . In both of these examples and indeed in all the examples thus far the repetition metacharacters or or 2 for example apply to the previous character or metacharacter. For example HTML developers often place nonbreaking spaces between words to ensure that text does not wrap between those words. Suppose .
