JavaScript learning process (1)

Basic Package Type: boolean,number,string.

Here are the main ways to talk about string:

1. Character method

The character methods of String are CharAt () and charCodeAt (), both of which accept only one parameter (based on the 0 positional parameter), charAt () returns the character at that position, and charCodeAt () returns the character encoding;

Example:

var stringvalue = "Hello World";

Alert (Stringvalue.charat (1));// output Letter E

Alert (Stringvalue.charcodeat (1));// Output 101, which is the character encoding of the letter E

2. String manipulation methods

String manipulation methods are concat (), Slice (), substr (), substring (),

Contcat () can return a new string to be stitched together

Example: var stringvalue = "Hello";

Alert (Stringvalue.concat ("World", "!")); / Output Hello world!

Slice (), substr (), substring () can accept two parameters

(1) When 1 parameters are accepted:

Example: var stringvalue = "Hello World";

Alert (Stringvalue.slice (3));// Output lo world

Alert (STRINGVALUE.SUBSTR (3));// Output lo world

Alert (stringvalue.substring (3));// Output lo world

(2) When 2 parameters are accepted

Example: var stringvalue = "Hello World";

Alert (Stringvalue.slice (3,7));// output lo w o position is at 7, so do not return

Alert (STRINGVALUE.SUBSTR (3,7));// output lo worl

Alert (stringvalue.substring (3,7));// output lo w

(3) where the parameter is negative

var stringvalue = "Hello World";

Alert (Stringvalue.slice ( -3));// output rld .... Explanation =-3+11 (string length)

Alert (STRINGVALUE.SUBSTR ( -3));// output Rld

Alert (stringvalue.substring ( -3));//Output Hello world ..... Convert all negative numbers to 0

Alert (Stringvalue.slice (3,-4));// output lo w

Alert (STRINGVALUE.SUBSTR (3,-4));// Output "", the method will be negative first plus string length, minus the second one converted to 0

Alert (stringvalue.substring (3,-4));// output Hel, this method converts all negative numbers to 0

4. Trim () method

Creates a string-by-body that returns characters before and after the deletion of a string, some browsers support Trimleft (), TrimRight ()

Example: var stringvalue = "Hello World";

Alert (Stringvalue.trim ());// Output Hello world

5. String Case Conversion

toLowerCase ()

toUpperCase ()

Tolocallowercase ()//For specific regions

Tolocaluppercase ()//For specific regions

6. String pattern Matching

Match () accepts only one parameter

7. Localcompare () method

JavaScript learning process (1)