将输入限制为仅特定字符和6位数字

Question

I want to restrict an input to only One Character (R) and 6 numbers only... Eg: R123896

If Input length increase 7 it will remove that digit and if First word is not R , it should replace that character to "R"

I have written this script, but don't know how to move forward and shape it to what i want...

$("#consultationident").keyup(function(key){
var txtVal = $(this).val();  
 if(isNumber(txtVal) && txtVal.length>6)
 {
     $(this).val(txtVal.substring(0,6) )
 }
});

Please help!

Answer 1

The use of a regular expression would be an idea...

 $("#consultationident").keyup(function(key){ // Uppercase the first character. var firstChar = $(this).val().substr(0,1).toUpperCase(); var rest = $(this).val().substr(1); $(this).val( firstChar + rest ); var txtVal = $(this).val(); var pattern = /^(R)(\\d{6})$/; // Check if the value entered fits the pattern. if(pattern.test(txtVal)){ console.log("Value ok"); }else{ console.log("Value wrong"); } }); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input id="consultationident"> 

Answer 2

here is the code for validating input using regex

 $("#consultationident").keyup(function(key){
    var txtVal = $(this).val();  
    if(txtVal.length>6)
     {
       str =  $(this).val().substring(0,7);

       pattern = /^[a-zA-Z]{1}(\d{6})$/



       if(pattern.test(str)) {
         str = str.replace(/^[a-zA-Z]/,"R")   // Replace any character with "R"
         console.log(str);
    }
      else {
         console.log("invalid input");
      }
   }
});