Built-in objects in js

Built-in objects in js
JavaScript charAt () function string. charAt (n) -- returns the character of the specified position (n)

• CharIs the abbreviation of character, Chinese "symbol, character"
• URL: http://www.dreamdu.com/javascript/string.charat/charat#syntax

  string.charAt(n);
  
  

  CharAt function parameters
  • N -- character position in the string (the first character of the string is 0) charAt function return value
    • Returns the n-Position Character.
      • If n is not between 0 and string. length-1, an empty string is returned.
      • JavaScript indexOf () function string. indexOf (substring, startpos) -- returns the position of substring in string.
        • Index, Chinese "Index"
        • URL: http://www.dreamdu.com/javascript/string.indexof/indexof#syntax

          string.indexOf(substring, startpos);

          IndexOf function parameters
          • Substring -- the substring to be searched
          • Startpos -- optional parameter. It is used to search for substring from the position of startpos of string. If this parameter is not available, the indexOf function return value will be searched from the start position of string.
            • Returns the position of the substring in the string.
            • The substring is not found in the string.-1 is returned.
            • JavaScript lastIndexOf () function string. lastIndexOf (substring, startpos) -- returns the position of the final match (appearance) of the substring in the string.
              • Last, Chinese "Last, last"
              • URL: http://www.dreamdu.com/javascript/string.lastindexof/lastindexof.pdf

                string.lastIndexOf(substring, startpos);
                
                

                LastIndexOf function parameters
                • Substring -- the substring to be searched
                • Startpos -- optional parameter. It is used to search for the substring from the startpos position of the string. If this parameter is not available, the return value of the lastIndexOf function is queried from the start position of the string.
                  • Returns the position where the substring matches the string.
                  • The substring is not found in the string.-1 is returned.

                    <script language="JavaScript" type="text/javascript">var myString="Welcome to Wrox books. ";myString=myString+"The Wrox website is www.Wrox.com. ";myString=myString+"visit the Wrox website today.";var foundAtPosition=0;var wroxCount=0;while(foundAtPosition !=-1){foundAtPosition=myString.indexOf("Wrox",foundAtPosition);if(foundAtPosition!=-1){wroxCount++;foundAtPosition++;}}document.write("there are+"wroxCount"+"occurrences of the word Wrox");</script>

                    
                    JavaScript substring () function string. substring (startPos, endPos) -- returns the string from the string's startPos position to the endPos position
                    • Substring, Chinese "substring"
                    • URL: http://www.dreamdu.com/javascript/string.substring/substring#syntax

                      string.substring(startPos, endPos);
                      
                      

                      Substring function parameters
                      • StartPos -- start position
                      • EndPos -- Return Value of the end position substring Function

                        String

                        JavaScript substr () function string. substr (startPos, length) -- returns the string whose length is length from the position of startPos of string.
                        • It does not comply with ECMA standards and is not in favor of use.
                        • Substr, Chinese "substring"
                        • URL: http://www.dreamdu.com/javascript/string.substr/substr#syntax

                          string.substr(startPos, length);
                          
                          

                          Substr function parameters
                          • StartPos -- start position (when a negative number is obtained, it is calculated from the end of the string)
                          • Length -- Return Value of the substr Function

                            String

                            JavaScript toLowerCase () function string. toLowerCase () -- returns a lowercase string
                            • LowerCase, Chinese "lower case"
                            • URL: http://www.dreamdu.com/javascript/string.tolowercase/tolowercase#syntax

                              string.toLowerCase();
                              
                              

                              Return Value of toLowerCase Function

                              Returns a lowercase string.

                              JavaScript toUpperCase () function string. toUpperCase () -- returns an uppercase string.
                              • UpperCase, Chinese "uppercase"
                              • URL: http://www.dreamdu.com/javascript/string.touppercase/touppercase#syntax

                                string.toUpperCase();
                                
                                

                                Return Value of the toUpperCase Function

                                Uppercase string

                                ToUpperCase function example

                                var str = "www.dreamdu.com";document.write(str.toUpperCase());
                                
                                

                                Result:

                                WWW.DREAMDU.COM