String and String

string

definition

A string is an immutable ordered sequence of 16-bit values, each character usually from the Unicode character set.
The length of a string is the number of 16-bit values it contains

literal

A sequence of characters enclosed in single or double quotes.
Single and double quotes can be nested, with strings delimited by the outermost quotes.

		如：“how are  ‘you’!”

String literals can be split into several lines. Each line must end with a backslash (\), and backslashes are not included in the content of the string.

let s = "how are \
"you";
console.log(s);

escape character

A character followed by a backslash (\) is used to express special meaning.

		如，\’，\”，\n，\r，\\等。

Universal escape characters
represent any character code in Latin-1 or Unicode through hexadecimal numbers.

 如：\xA9，表示Latin-1编码的版权符号。“\xA9”->”©”
 如：\u03C0，表示Unicode编码的π字符。"\u03c0"->”π”

Common methods

1.str.split(seperator, limit) // Split the string into an array

把一个字符串分割成字符串数组(不改变原字符串)
 seperator(可选)，指定字符串或正则
  limit(可选)，指定数组的最大长度

2.str.substring(start, end)：//Intercept string

参数均为正，返回从start到end-1的字符，不改变原字符串

3.str.slice(start, end)：//Intercept string

两个参数可正可负，负值代表从右截取返回从start到end-1的字符，不改变原字符串

4.str.substr(start, length): //Intercept string.
The start parameter can be positive or negative. A negative number means intercepting from the right without changing the original string.
5. toUpperCase(): //Convert all strings to uppercase
6 , toLowerCase(): //Convert all strings to lowercase
7, str.replace(rgExp/substr, replaceText): //String replacement

返回替换后的字符串，不改变原字符串

8. str.lastIndexOf(searchString, startIndex): //Find string

从右往左查找，无目标字符时返回-1

9. str.indexOf(searchString, startIndex)：//Find string

返回字符串第一次出现的位置，从startIndex开始查找，无目标字符时返回-1

10. str.concat(str1, str2)//String concatenation

将str1和str2字符串拼接起来，不改变原字符

11. str.trim(): //Remove spaces before and after the string


var foo = ' bar ';
console.log('('+str.trim()+')');  //(bar)