Introduction

In your HTML page add the control you want to validate but for this sample, I used textbox to demonstrate this code, in my textbox control I used onkeyup event to validate whether recently entered character is numeric or not. so you can call this JavaScript code as your requirement in your project.
Test.html
  1. <input type="text" id="txt" name="txt" onkeyup="txtValidate(this.id)"/>
JavaScript Code
  1. function txtValidate(txtid)
  2. {
  3. var ok = 0;
  4. var a = document.getElementById(txtid).value;
  6. for (var i = 0; i <= a.length - 1; i++)
  7. {
  8. var j = a.charCodeAt(i);
  9. for (var k = 48; k <= 57; k++)
  10. {
  11. ok = 0;
  13. if (k == j)
  14. {
  15. ok = 1;
  16. break;
  17. }
  18. }
  20. }
  22. if (ok == 0)
  23. {
  24. alert("Only Numeric Values Allowed");
  25. document.getElementById(txtid).value = "";
  26. for (var i = 0; i < a.length - 1; i++)
  27. {
  28. var j = a.charCodeAt(i);
  29. for (var k = 48; k <= 57; k++)
  30. {
  31. ok = 0;
  33. if (k == j)
  34. {
  35. document.getElementById(txtid).value += a.charAt(i);
  36. }
  37. }
  39. }
  40. }
  41. }
I hope this code helps you. Thank you.