JS Study notes Second article

JS Note Finishing

1, Stringapi

A) uppercase and lowercase conversions: str.touppercase (); Str.tolowercase ();

b) Get the specified position character:

1. Str[i]---> Countdown second str[str.length-2]
2. Str.charat (i)
3. Str.charcodeat (i); return Unicode of characters?

c) Find the location of the keyword:

I.var i=str.indexof ("KWord" [, Starti]); return -1,starti default is 0 if not found

Ii var i=str.lastindexof ("KWord" [, Starti]); Find the first keyword that appears to the left of the Starti location Statri default is Length-1

d) Get substring:

I var substr=str.substring (starti[,endi+1]);

Ii var substr=str.substring (starti[,endi+1]); Negative parameters are not supported

Iii var substr=str.substring (Starti, take several);

Example: Get the user name and domain name.

Function () {

Var i=email.indexof ("@");

Var Username=email.slice (0,i);

Var Domain=email.slice (i+1);

Alert ("User name" +username);

Alert ("Domain name" +domain);

}

<button onclick= "Mail (Prompt (' Enter mailbox ')" > enter mailbox <button>

2. String API 2

A) delimited string: var arr=str.split ("delimiter");

1. Each string is saved as an array in arr.
2. Fixed routines: Cutting a string into a character array: var chars=str.split ("");
   1. Example: var a= "Hello";

var chars=a.split ("");

Console.log (chars);

Iii Pattern matching: 2 types

1.var I=str.search (/keword/i); only from the start position, Zhao first matches the keyword.

2.var Arr=str.match (/kword/ig);

A) The contents of all keywords are saved in arr

b) Arr.length indicates the number of matched keywords

c) * If not found, return to null*

d) * All must first determine whether is NULL, again processing! *

3.Var newstr=str.replace (mode, "replace content");

Examples:

var kword=/no/ig;

var reply=prompt ("input reply");

var arr=reply.match (KWord);

Reply=reply.replace (KWord, "* *");

alert (reply);

Alert ("Total substitution" + (arr?arr.length:0) + "place");

2. Regular Expressions:

A) An expression that specifically specifies the formatting rules for characters in a string format.

b) When to use: the regular expression is used whenever a string formatting rule is defined.

c) predefined character set: \d ==>[0-9] one digit

1. \w ==>[0-9a-za-z];1 digits, letters, or underscores.
2. \s = = "[null character] represents a null character: a space, tab character.
3. . All other characters except line break.

d) quantifier: Specify the number of times a character set appears: 2 kinds

Definite quantity: 3 kinds: {Min,max}: Min bit, max bit

{min,}: Min bit at least

{n}: Must be N-bit

ID Number: At least 15 digits

2-digit number

Last digit or x x

The latter three bits are optional, but appear up to 1 times

\D{15} (\d{2}[0-9xx])?

Number of uncertainties: 3:

? ==>{0,1}: Optional, up to 1 times

*==>{0,}: Optional, more than an unlimited number of

+==>{1,}: At least once, more than an unlimited number of

Phone Number: +86 or 0086 optional, up to 1 times

Empty characters are optional, more than the number of unlimited

1

Choose one from 3,4,5,7,8

Must be 9 digits in the end.

(\+86|0086)? \s*1[34578]\d{9}

JS Study notes Second article