使用JavaScript检查字段是否为数字

Posted 2021-02-26

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

function checkNum(){
 
	var inputBox = document.getElementById('abc');
	if(inputBox.value.length!='0'){
	var j=0;
	var run = false;
	for(j=0; j<inputBox.value.length; j++){
	  var char=inputBox.value.charAt(j);
 
	    if(inputBox.value.charAt(j)>='0' && inputBox.value.charAt(j)<='9'){
	     run = true;
	    }
		    else{
		    run = false;
		    alert("Q# can only be a numeric value");
		    document.getElementById('abc').focus();
			document.getElementById('abc').value="";
			break;
			}
	}
	if(run){
 
	alert("The field has been successfully validated!");
	}
 
 
	}
	else if(inputBox.value.length == '0'){
	alert("Please enter a Q#");
	document.getElementById('abc').focus();
	}
}