JavaScript Basics - String

Learning a good foundation is the foundation of learning a language well. Let’s organize String and encourage them to learn together.

String is different from string. String is a constructor and string is a type of variable. (string is an instance of String)

Use it after declaring a string, var str = "wo shi yi ge hao xue sheng"

Whether it contains

① Determine whether a string is contained in another string, including return true, and does not include return false (searchStr,formIndex). SearchStr The query starts from where the string formIndex included.

('wo') //true

Cut string

① Get a certain segment of the string and return a new string (start, end). If start is a negative number, it will be treated as start+, the same as end.

 (-2) //ng

② Cut the string into an array and return an array (separator, howmany) separator can be a string or a regular expression, howmany is the length of the cut array

 (/i/g) //["wo sh", " y", " ge hao xue sheng"]

③ Get a certain number of characters from the beginning of the string subscript and return a new string (start, length) start can be a negative number. If it is a negative number, it is the index of the reciprocal number.
  

(-2) //ng

④ Extract characters (start, end) start, end non-negative integers in the string

 (1,2) //o

Find the location of the string | Whether it exists

① Find whether a character exists. It will return to the location where it first appears. If it does not exist, it will return -1. FromIndex is an optional option. If it does, it will start to check from a certain index position (searchStr, fromIndex)

 ('shi') //Return to the first appearance position, 3 ('shi',8) //return-1

('shi') //Return to the last occurrence position, 3('shi',2) //Return -1

③ Query the match of regular expressions in a string, return an array, and return null cannot be found. If the parameter is not a regular, it will be forced to convert to regular (RegExp)

 (/[1-9]/g) //null
 (/\d/g) //["w", "o", "s", "h", "i", "y", "i", "g", "e", "h", "a", "o", "x", "u", "e", "s", "h", "e", "n", "g"]

④ Return the index of the first character of the substring matching the regular expression, without returning -1 (RegExp)

 (/wo/g); //0

About encoding

① Return to the encoding of a certain location (index)

 (1) // Return the encoding of the position with index 1, 111

②Create a string through some encoding ()
   

 (111) //The compiled string is o

Related location

① Return the character at a certain position (index)
  

 (1) // Return the character with index 1, o

Replace text

①.Replace text matching regular expressions (RegExp, str)

(/hao/g,'huai') //wo shi yi ge huai xue sheng

②. Remove the spaces in the two segments of the string and return the new string ()

There are also those who write concat() to connect strings. The only benefit I can think of is that I write less + sign connectors. When it comes to concat(), I think of what to do if repeat() is... (num)

I hope this article will be helpful to everyone's JavaScript programming.