javascript - Table Cell loop produces undefined index erroneously -

$('#process').click(function() {     var char_matrix = [];     $('#char_input tr').each(function(e) {         $(this).children('td').each(function() {             var = $(this).css('background-color').replace(/\d+/g, '');             if (a === '2551650') {                 char_matrix[e] += "0";             } else {                 char_matrix[e] += "1";             }//end if         });//end each         alert(char_matrix[e]);     });//end each });//end func 

this code loops through each table row, , each row cell create array of 1's , 0's. each index of array different row, , each index composed of series 1's , 0's indicating background color status of each row. expected output like:

10101010 10101010 10101010 10101010 10101010 10101010 10101010 10101010 

actual output is:

undefined10101010 undefined10101010 undefined10101010 undefined10101010 undefined10101010 undefined10101010 undefined10101010 undefined10101010 

i have no idea causing each row have undefined @ beginning, , quite annoying. undefined index added array, in addition correct 8 binary values. have tried defining char_matrix global , local variable no avail.

i realize can use straight javascript, not option me on project.

after line

$('#char_input tr').each(function(e) { 

add line

  char_matrix[e] = "" 

otherwise char_matrix[e] undefined. consistent results since

undefined + "1" === "undefined1"