How to understand regex '\b'?
javascript, regex, string
Solution
The `\b` matches position, not a character. So this regex `/end\bend/g` says that there must be string `end`. Then it should be followed by not a word character, which is `,` and it matches, but the regex engine doesn't move in the string and it stays at `,`. So the next character in your regex is `e`, and `e` doesn't match `,`. So regexp fails. Here is step by step what happens:
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/end\bend/g, "end,end" (match)
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/end\bend/g, "end,end" (both regex and string position moved - match)
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/end\bend/g, "end,end" (the previous match was zero-length, so only regex position moved - not match)
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Problem
I am learning the regex.But I can't understand the '\b' , match a word boundary . there have three situation,like this: - Before the first character in the string, if the first character is a word character. - After the last character in the string, if the last character is a word character. - Between two characters in the string, where one is a word character and the other is not a word character. I can't understand the third situation.for example： ``` var reg = /end\bend/g; var string = 'wenkend,end,end,endend'; alert( reg.test(string) ) ; //false ``` The '\b' require a '\w' character at its one side , another not '\w' character at the other side . the string 'end,end' should match the rule, after the first character is string ',' , before the last character is string ',' , so why the result is error .Could you help,Thanks in advance! ============dividing line============= With your help, I understand it. the 'end,end' match the first 'end' and have a boundary ,but the next character is ',' not 'e',so '/end\bend' is false. In other words ,the reg '/end\bend/g' or others similar reg aren't exit forever. Thanks again