jquery - How check array by index -


i want write simple example, count messages. very important: need check if array null or not using index, (main_arr[0]):

<body>  <input type="button" id="btn1" name="click" value="click"/> <script type="text/javascript"> $(document).ready(function () { var main_arr ;  $("#btn1").click(function () {  if (main_arr[0] == null) {     main_arr = [];     alert("array initialized!");  } else {     main_arr.push("message");     alert("in array " + main_arr.length + " messages!"); }  });   }); </script>  </body>

how check if main_arr[0] have value?

try

is 'main_arr' defined?

if (typeof main_arr != "undefined") { }

does 'main_arr' has elements?

if (main_arr.length > 0) { }

so code becomes

$(document).ready(function () {     var main_arr;      $("#btn1").click(function ()     {         if (typeof main_arr == 'undefined')         {             main_arr = [];         }          if (main_arr.length > 0)         {             // has elements. time check '0th' element         }         else         {             // no elements. push one.             main_arr.push('message');         }      }); });

hope helped.


Comments

Post a Comment