The string object for getting started with javascript [a must-read for newbies]

1. String object

String object is used to process text (string).

2. Constructor

new String(value) // Constructor function
function String(value) // Conversion function

3. Attribute

length The number of characters in the string

var str = new String("abcdefg");
document.write(str.length);   //输出 7

4 , Method

　1. chatAt()　Remove the character at the specified position in a string.

var str = new String("abcdefg");
document.write(str.charAt(1));   //输出 b

2. chatCodeAt() Returns the code of the character at the specified position in a string.

var str = new String("abcdefg");
document.write(str.charCodeAt(1));   //输出 98

3. concat() Concatenate one or more values ​​into a string.

var str = new String("abcdefg");
var str1 = "hijk";
document.write(str.concat(str1));   //输出 abcdefghijk

4. indexOf() Find the position of a character or string in the specified string. If not found, return -1

　 Syntax: indexOf(str) str: substring or character

　 indexOf(str,start) str: substring or character. start: Specify the starting position of the search

  var str = new String("abccba");
  document.write(str.indexOf('b'));   //输出 1
document.write(str.lastIndexOf("bc"));   //输出 1

Use this method to achieve the Contains effect and determine whether a string contains another string:

<script type="text/javascript">
    window.onload = function () {
      var str1 = "刘备";
      var str2 = "刘备是个牛人!";
      alert(str2.indexOf(str1)); //输出 0 出现的位置
      if (str2.indexOf(str1) > -1) {
        alert("包含!");
      }
      else {
        alert("不包含!");
      }
    }
  </script>

5. lastIndexOf() In the specified string Find the position of a character or string backwards (in reverse order). If not found, return -1

　 Syntax: lastIndexOf(str) str: substring or character

　 lastIndexOf(str,start) str: substring or character. start: Specify the starting position of the search

var str = new String("abccba");
document.write(str.lastIndexOf('b'));   //输出 4

6. localeCompare() Use the locally defined order to compare strings.

var str = "abccba";
document.write(str.localeCompare("bc"));　　//输出 -1

7. match() Use regular expressions to perform pattern matching.

　8. replace()　 Use regular expressions to perform search and replace operations.

var str = "abccba";
document.write(str.replace("b","-"));　　//输出 a-ccba

9. search() Find a string matching a regular expression in a string.

var str = "abccba";
document.write(str.search("b"));  //输出 1

10. slice() Returns a slice or string of string. If the parameter is a negative number, it means counting from back to front. The original string is not changed.

var str = "abcdefg";
document.write(str.slice(2) + "<br/>"); //输出cdefg
document.write(str);          //输出abcdefg　　可以看到原字符串并没有更改。

11. split() Split with the specified delimiter string or regular expression and return a string array.

var str = "abcdefg";
var arr = str.split("d");
document.write(arr.join());          //输出abc,efg

12. substr() Extract a substring of the string, a variant of substring(). Deprecated.

　13. substring() Extract a substring of the string.

　 Syntax: substring(start,end) Starting from start and ending at end, including start but excluding end. The original string is not changed.

var str = "12345678";
document.write(str.substring(1,4));　　//输出 234

14. toLowerCase() Returns a lowercase copy of the specified string.

var str = "abcDEF";
document.write(str.toLocaleLowerCase());  //输出 abcdef

15. toString() Returns the original string value.

var str = "abcDEF";
document.write(str.toString());  //输出 abcDEF

16. toUpperCase() Returns an uppercase copy of the specified string.

var str = "abcDEF";
document.write(str.toUpperCase());  //输出 ABCDEF

17. trim() Returns a copy of the specified string with leading and trailing whitespace removed.

var str = "  abcDEF  ";
document.write("11" + str.trim() + "11" + "<br/>");  //输出 11abcDEF11
document.write("11" + str + "11");  //输出 11 abcDEF 11

　18. valueOf() Return the original string value.

var str = "abcDEF";
document.write(str.valueOf());  //输出 abcDEF