Variable is undefined in function

Question

I have a string with comma separated values:

var newVal = "9103174091,1231231232"
$(ctrl).val(DataReview.Encryption.formatPersonNmbr(newVal));

I call a function with this value:

function (val) {

        val = val.split(",");
        var newVal = "";
        for (var i = 0; i <= val.length; ++i)
        {
            val[i] = val[i].replace(/ /g, '');
            var newVal = val[i];

            if (val[i].length == 10 || val[i].length == 11 || val[i].length == 12) {
                if (val[i].length == 11) {
                    val[i] = val[i].substring(0, 6) + val[i].substring(7);
                }
                if (val[i].length == 10) {
                    var year = '20' + val[i].substring(0, 2);
                    var month = val[i].substring(2, 4);
                    var day = val[i].substring(4, 6);
                    var date = new Date(year, month - 1, day);

                    if (isNaN(date) == false) {
                        var currentDate = new Date();
                        if (date > currentDate) {
                            val[i] = '19' + val[i];
                        } else {
                            val[i] = '20' + val[i];
                        }
                    }
                }
            }

            newVal += val[i].substring(0, 8) + '-' + val[i].substring(8);   
        }

        return newVal;
    }

When I run this, I get the following error:

TypeError: val[i] is undefined
val[i] = val[i].replace(/ /g, '');

I can't understand how this can be undefined? What am I doing wrong?

Answer 1

Are you sure this is the correct end condition for your for loop?

for (var i = 0; i <= val.length; ++i)

Or did you mean this:

for (var i = 0; i < val.length; ++i)

This might be caused by 1-off errors. Accessing the element after the last element evaluates to undefined .

Example

var list = [2, 4, 6, 8];

for (var i = 0; i <= val.length; i++){
  console.log(list[i]);
}

Output

2
4
6
8
undefined

The last occurence is undefined because there is no value at val[4] , values in the list are accessible only up to val[3] . Its index reaches 4 because val.length returns 4, because there are four elements. Using the less than or equal operator to allows this error to occur.