[jQuery] joining arrays

I want to join the results of one array to another, i.e. i want one
array containing a list of all salary and bonus ids... am i missing
something? i tried merge and couldnt get that to work. have googled
extensively and it seems the javascript concat function does what i
need but am getting object doesnt support this function or method
error when using concat as below.

var context = $('#employees')[0];
var arr1 = $("tr td input[id$='Bonus']", context).map(function()
{ return $(this).attr("id"); });
var arr2 = $("tr td input[id$='Salary']", context).map(function()
{ return $(this).attr("id"); });

arr1 = arr1.concat(arr2);

$.each(arr1, function() {
alert(this);
});

many thx