Foreign language translation--javascript Tutorial--regular expression--(2)

character class

Suppose we want to find a number in the string. Not the specified number, but any number, for example: Find "1" in "Only 1", and look for "5" in "Give me a 5".

Substring matching can be used in loops to find all the numbers in 0-9. However, the use of a regular formula can be handled more gracefully.

Regular can use character classes instead of specific characters.

For example, a regular uses "\d" to represent any number. The following example matches a number:

1 showmatch ("I ' m 5 yearsold",/\d/)   //  5

The most commonly used character classes are:

Any number in the \d:0-9;

\s: whitespace characters, such as tab indentation, line breaks, and so on;

\w: Latin alphabet, numerals or underscores;

A regular may include the character class and the normal tag together:

1 showmatch ("I ' m the 1stOne",/\dst/)   //  matches ' 1st '

The following code has a regular formula that contains several character classes together:

1 showmatch ("I ' M 1",/\d\s\w\w\w\w/)   //  1 year

There are also some antisense character classes:

\d: Non-digital;

\s: non-whitespace characters;

\w: Non-Latin alphabet, numerals or underscores;

For example, find the first non-alphabetic character:

1 showmatch ("I ' M 1year old",/\w/)   //  matches apostrophe '

A regular can also contain non-printable string characters: \ n (line break), \ t (tab), and so on. These are obviously just characters, not character classes.

Space is very important!

Normally, we don't care about spaces. "1-5" and "1-5" look no different.

However, in a regular style, spaces and other identities are the same .

The following regular mode does not work correctly because there is no space identifier included:

1 showmatch ("1-5",/\d-\d/)  //  no matches!

Let's change it. We can put the space mark in the regular formula, or it is best to include the space in it:

1 showmatch ("1-5",/\d-\d/)   //  works2 showmatch ("1-5//  also works3 showmatch ("1-5//   fails! (no spaces in string)

The last match failed because there are no spaces in the example. So don't put extra spaces in the regular, they all make sense.

In the regular style, the point " . " means any character other than the line break:

1 showmatch ("a char//  " char "2 showmatch ("a ch-r// "Ch-r" 3 showmatch ("a ch R//  " Ch R ", the space is also a char

Although the point " . " can represent all characters, it must have characters:

1 showmatch ("A chr// not found

Foreign language translation--javascript Tutorial--regular expression--(2)