I guess you have code like this:

var textarea1 = $(#textarea1);

textarea1.val() returns undefined if the element is not found (i.e. an element with ID textarea1). Check if you haven't made a typo in the element selector and if the function is called after the element is available.

This function works for strings and arrays containing strings. If an argument or array value is not a string nor an array, it does not touch the value.

function maskData(input) {

    // edit strings

    if (typeof input == string) return input.replace(/ss+/, );



    // if 'input' is an array, iterate through its elements and pass it to maskData again

    if (input instanceof Array) {

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

           input[i] = maskData(input[i]);

        }

        return input;

    }

    // otherwise just return itself untouched

    return input;

    // alternative: return an empty string

    //return ;

}

If your intention is to turn multiple whitespace to a single one (as in string with multiple spaces in it -> string with multiple spaces in it), you could also use the simplified RE:

/s+/g

A single whitespace character will be replaced by a single space. Multiple whitespace characters will also be replaced by a single space. Note that I added the g flag so the replacement occurs multiple times.