Javascript basics-String, javascriptstring

Javascript basics-String, javascriptstring

The foundation for learning a good language is the foundation for learning a good language. Below we will organize strings to encourage you 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)

Declare a string and use it. var str = "wo shi yi ge hao xue sheng"

Include or not

① Determine whether a string is included in another string. If true is returned, false str. includes (searchStr, formIndex) is returned. If false is exclusive, the position where formIndex starts to be queried.

str.includes('wo') //true

Cut string

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

 str.slice(-2) //ng

② Cut the string into an array and return an array str. split (separator, howator) separator which can be a string or a regular expression, and howator which is the length of the cut Array

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

③ Obtain a certain number of characters starting from the string subscript and return a new string str. substr (start, length) start which can be a negative number. If it is a negative number, it is the reciprocal index.

str.substr(-2) //ng

④ Extract the str. substring (start, end) start and end non-negative integers between two specified subscripts.

 str.substring(1,2) //o

Locate the string | whether the string exists

① Check whether a character exists and the location where the first occurrence is returned.-1 is not returned. fromIndex is an optional option. If yes, check str from an index position. indexOf (searchStr, fromIndex)

Str. indexOf ('shi ') // returns the first occurrence location, 3 str. indexOf ('shi', 8) // returns-1

② Return the final position of the specified string. From the back-to-back search, fromIndex is the start index str. lastIndexOf (searchStr, fromIndex)

Str. lastIndexOf ('shi ') // returns the last occurrence location, 3str. lastIndexOf ('shi', 2) // returns-1

③ Query the matching of regular expressions in a string, return an array, and return null if not found. If the parameter is not a regular expression, it is forcibly converted to regular str. match (RegExp)

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

④ Returns the index of the first character of the substring that matches the regular expression.-1 str. search (RegExp) is not returned)

 str.search(/wo/g); //0

Encoding

① Return the str. charCodeAt (index) encoding at a location)

Str. charCodeAt (1) // returns the encoding of the location where the index is 1, 111

② Use some encoding to create a String. fromCharCode ()

String. fromCharCode (111) // The compiled String is o

Location-related

① Return the character str. charAt (index) at a certain position)

Str. charAt (1) // returns the character at the position where the index is 1, o

Replace text

①. Replace the text str. replace (RegExp, str) that matches the Regular Expression)

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

②. Remove the spaces of the two strings and return the new string str. trim ()

There is also a concat () connection string. The only benefit I can think of is that I write a few less + number connectors. When it comes to concat (), I think about repeat .... str. repeat (num)

I hope this article will help you design javascript programs.