How can I capture "undefined" in javascript?

Question

I'm working on going through all values in a form but I keep getting undefnined then my values show up. I'm dynamically creating the form so I think the undefined maybe coming from the blank field.

Here's the code I'm using to get all the elements:

//try to get all elements
var output;
$(this).parents('form') // For each element, pick the ancestor that's a form tag.
.find(':input') // Find all the input elements under those.
.each(function(i) {
    //alert(this.value+ " = " + i);
    if (typeof this.value === "undefined") {
        output = "nothing here";
    } else {
        output += this.value;
    }
});
$("div#total").append("value = " + output + "<br>");

If I enter 1,2,3,4,5,6 then my output is:

hello value = undefined
value = undefined1
value = undefined1
value = undefined12
value = undefined12
value = undefined123
value = undefined123
value = undefined1234
value = undefined1234
value = undefined12345
value = undefined12345
value = undefined123456

The result is what I want except for the undefined part. I saw this answer: JavaScript: undefined !== undefined? and have tried their suggestions but I can't seem to get my program to save the value if the value is NOT undefined.

If it helps here's the full code: http://jsfiddle.net/lostsoul/rKLrZ/

user1106925 · Accepted Answer · 2012-07-13 03:48:33Z

3

Initialize output to an empty string.

var output = "";

If an input has no value, it'll give you an empty string instead of undefined.

answered Jul 13, 2012 at 3:48

user1106925

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Comments

xiaowl · Accepted Answer · 2012-07-13 04:00:22Z

0

Uninitialized var output actually has a value undefined.

var output; // Value of output is undefined
output += "2"; // undefined + "2" ->  "undefined2"

answered Jul 13, 2012 at 4:00

xiaowl

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