Computer to pick up from the doll---------Regular expression (study note i)

This article is mainly to the regular, learning new things, I remember the teacher said a good way, to take questions to learn, not light to see the theory, you have to always think of this thing is what, how to use, where, I think the said is very good. So always think about these questions when you look at them.

This is the meow of the study notes may have a lot of shortcomings, I hope you can more comments!

Let's go, Class!

What is a regular expression?

Regular: Also called rules, can let the computer read the rules of Human.

(Note: The regular are all manipulation strings)

A regular notation:

var re =/a/; Write two here//the system will think this is a comment, so it's best to write something.

var re = new RegExp (' a ');

The default is case-sensitive in regular, if not case-sensitive, at the end of the regular ID I

Regular default: The regular match succeeds and the match is not continued. If you want to find all you need to add the identity G (Global match)

Common methods:

1)

Test: Regular to match string, if the match succeeds returns true, the failure returns false.

The notation for test: Regular. Test (string);

eg

var str = ' abcddef ';

var re =/b/;

Alert (Re.test (str));

This will return ture, because the matching B is required in the string;

What if the matching BC? (will also return ture)

What if the matching BD? (Will return FALSE, because BD is not a whole)

Escape characters:

\s: Space

\s: Non-whitespace

\d: Digital

\d; non-digital

\w: Characters (Letters, numbers, underscores)

\w: Non-self-character

2)

Search: Matches the string, if the match succeeds, returns the successful position, and returns 1 if the match fails.

The wording of search: string. Search (regular);

eg

var str = ' abcdef ';

var re =/b/;

Alert (Str.search (re));

Apparently found it. So return-1;

If you write like this

var re =/b/

Run again

Str.search (re);

Return is-1, you can see that the default is case-sensitive in the regular;

3)

Match: Matches the string, if the match succeeds, returns an array of successful matches, and returns null if the match is unsuccessful;

Match's notation: string. Match (regular);

eg

var str = ' Jdl46d4a6sd464sd4w4a4f6 ';

var re =/\d/;

Alert (Str.match (re)); [4];

There is only one [1] followed by a lot of numbers that are not added to the array, why?

This is the default behavior of the regular

Regular default: The regular match succeeds and the match is not continued. If you want to find all you need to add the identity G (Global match)

This will be written in the following form:

var re =/\d/g;

var str = ' Jdl46d4a6sd464sd4w4a4f6 ';

var re =/\d/g;

Alert (Str.match (re)); [4,6,4,6,4,6,4,4,4,4,6];

Each of these is added to the array separately, and if I want to make a group of sequential numbers, how can i solve them?

In general, you may think

var re =/\d\d/g;

Write like this

If the number is not certain, so write ... Have flaws

This is the time to use the quantifier (my God, so magical?)

Quantifier: Match an indeterminate position

+: appears at least once

var re =/\d+/g; That means the number appears at least once.

4)

Replace: Regular to match string, match successful character to replace with new string

How replace is written: string. Replace (regular, new string)

eg

var str = ' AAA ';

var a =/a/;

str = str.replace (Re, ' B ');

alert (str);

The result is ' BAA ';

Because the program matches to the first a after the first A is replaced with B; What if I want all a to be replaced by B? What should I do?

var re =/a/g;

So all A is replaced by a B? You can try it yourself can rely on the knowledge of the previous realization;

I will write some actual chestnuts in the back, although most of them are carried. Because it is a study note, I will do some original article although not necessarily the technology

Computer to pick up from the doll---------Regular expression (study note i)