Question

Is there some way that I can run the following:

var data = $("#dataTable").data('timer');
var diffs = [];

for(var i = 0; i + 1 < data.length; i++) {
    diffs[i] = data[i + 1] - data[i];
}

alert(diffs.join(', '));

Only if there is an attribute called data-timer on the element with an id of #dataTable?

Answer 1

if ($("#dataTable").data('timer')) {
  ...
}

NOTE this only returns true if the data attribute is not empty string or a “falsey” value e.g. 0 or false.

If you want to check for the existence of the data attribute, even if empty, do this:

if (typeof $("#dataTable").data('timer') !== 'undefined') {
  ...
}