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To check whether a field is numeric by using JavaScript

/ Published in: JavaScript
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This snippet contains a text input field called 'abc' and we calling the checkNum function as the onclick action of a button 'btn'

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Copy this code and paste it in your HTML 
  1. function checkNum(){
  2.  
  3. 	var inputBox = document.getElementById('abc');
  4. 	if(inputBox.value.length!='0'){
  5. 	var j=0;
  6. 	var run = false;
  7. 	for(j=0; j<inputBox.value.length; j++){
  8. 	  var char=inputBox.value.charAt(j);
  9.  
  10. 	    if(inputBox.value.charAt(j)>='0' && inputBox.value.charAt(j)<='9'){
  11. 	     run = true;
  12. 	    }
  13. 		    else{
  14. 		    run = false;
  15. 		    alert("Q# can only be a numeric value");
  16. 		    document.getElementById('abc').focus();
  17. 			document.getElementById('abc').value="";
  18. 			break;
  19. 			}
  20. 	}
  21. 	if(run){
  22.  
  23. 	alert("The field has been successfully validated!");
  24. 	}
  25.  
  26.  
  27. 	}
  28. 	else if(inputBox.value.length == '0'){
  29. 	alert("Please enter a Q#");
  30. 	document.getElementById('abc').focus();
  31. 	}
  32. }

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