quantifier
| quantifier | description |
|---|---|
| n+ | Matches any string of at least one n. |
| n* | Matches any string contains zero or more occurrences of n. |
| n? | Matches any zero or a string containing n. |
| n{X} | Matching string comprising the sequence of X n. |
| n {X, Y} | It contains the string matching sequences X or Y is a n. |
| n{X,} | X matching string comprising at least a sequence of n. |
| n$ | Matches any string of n ends. |
| ^n | Matches any string that begins with n. |
| ?=n | Immediately followed by the specified string matches any character string n. |
| ?!n | Immediately thereafter not match any character string specified string n. |
/ *
* Create a regular expression used to check whether a string contains ab &
*
* quantifier
* - number of times a content can be provided by the quantifier occurrence
* - valid only for a quantifier content in front of him
* - {} occurring just a few mean
* - {m, n} m to n times appear content
* - (ab &) and the content can be set as a
* - {3} occurs three or more times the contents
* /
N is the n +: + is at least equivalent to a mean {1}
Is the n * n: Number * means zero or more, corresponds to {0}
Regular n? They are:? 0 or one equivalent, equivalent to {0,1}
^ A with a check string does not start with a
Check with a & ends in a string is not
If the regular use both ^ & string that represents full compliance with regular expressions
Practice writing a detected phone number regular expression!
/ *
* Create a regular expression to check if a string is a valid phone number
* regular phone number:
* 18136511586
* 1. outset
* 2. The second digit is any number 3-9
* 3. after three is an arbitrary number 9
* /
