JS to determine whether the string contains numbers, English letters, Chinese characters

 1, use JS to determine whether a string contains numbers, English letters, Chinese characters 
 String str = "This is  string "; 
 1> 
 var a =/[0-9]/; 
 var b = a.test (str ),//true, indicating a number 
 2>  
 var a =/[a-z]/i; 
 var b = a.test (str ),//true, indicating the English alphabet 
 3> 
  var a = new RegExp (" [\\u4e00-\\u9fff]+ "," G "); 
 var B = a.test (str)  ;//true, description     
 4> 
 var a =/[0-9a-z]/i; 
 var b = a.test (str)//true, description  have English letters or numbers  

 2, judging string length 
 String str = "This is  
 1> does not contain Chinese characters 
 var len = str . length; 
 2> the number of characters in a string of pure Chinese characters 
 var a =/[\u4e00-\u9fa5]/g; 
 var len = Str.match (a). length; 
 3> in English mixed string length, English characters plus 1, Kanji plus 2 
 function strlen (str) {
     var len = 0; 
     for (var i=0; i<str.length; i++) {
      var c = str.charcodeat (i); 
    //single byte plus 1 
      if ((c >= 0x0001 && C <= 0x007e) | | (0xff60<=c && c<=0xff9f)) {
        len++; 
     } 
      Else {
//Kanji plus 2 
       len+=2; 
      
    } 
     return len; 
} 
 
 var len = strlen (str); 
  

JS to determine whether the string contains numbers, English letters, kanji