JS条件语句不起作用

Question

My if statement doesn't appear to be working when checking for nonnumberic inputs on the weight variable, upon submitting. Why is this?

   submitBtn.onclick = function(){

    var name = document.getElementById('name').value;
    var weight = document.getElementById('weight').value;
    var pound = weight * 2.20462;

    //Check that the value is a number
    if(isNan(weight)){
     alert("Please enter a number);
    }
   }

Here it is in JsFiddle link

Answer 1

There are multiple issues in your code:

• You attempt to call .onclick on submitBtn , which is undefined.
• You attempt to call .isNan() which should be .isNaN()
• You don't close the string passed to your alert() function:

//Define submitBtn
var submitBtn = document.getElementById('submitBtn');
submitBtn.onclick = function(){

    var name = document.getElementById('name').value;
    var weight = document.getElementById('weight').value;
    var pound = weight * 2.20462;

    //Call isNaN()
    if(isNaN(weight)){

        //Close your string
        alert("Please enter a number");
    }
}

JSFiddle

Answer 2

You might should use isNaN

submitBtn.onclick = function(){

    var name = document.getElementById('name').value;
    var weight = document.getElementById('weight').value;
    var pound = weight * 2.20462;

    //Check that the value is a number
    if(isNaN(weight)){
       alert("Please enter a number");
    }
}