html - Jquery show number within div in alert -

hi

i want show number in div in alert this

<script>  var sec = $('#demo').html(); alert(sec); </script>  <div id="demo">100</div> 

code show 100 number

but null or undefined or 0 when use

size(); , text(); , html(); , length; 

edit : got problem . jquery v1.7.1 , seems has problem . upgraded jquery v1.9.1 , code works fine . thank answers

set

this techniques set (place) number inside empty <div id="demo"></div>

$('#demo').text(100);      // overwrite new content $('#demo').html(100);      // overwrites + can insert raw (string) html.  $('#demo').append(100);    // keeps content , appends element $('#demo').prepend(100);   // keeps content , prepends element $('#demo')[0].textcontent = "100"; // jq/js, overwrite text content $('#demo')[0].innerhtml = "100";   // jq/js, overwrite html document.getelementbyid('demo').innerhtml = 100 ; // pure js example 

http://jsbin.com/eyuhay/10/edit

get

this techniques get desired content (100) out of <div id="demo">100</div>

var number = $('#demo').text();            // jq                   var number = $('#demo').html();            // jq var number = $('#demo')[0].innerhtml;      // jq/js var number = $('#demo').get(0).innerhtml;  // jq/js using .get(0) instead of [0] var number = document.getelementbyid('demo').innerhtml;   // pure js var number = document.getelementbyid('demo').textcontent; // pure js 

http://jsbin.com/eyuhay/11/edit

.size(), length

.size() jquery method retrieve number of elements in our object array.
.length native js method the... length :-d

additionally take @ : http://jsbin.com/eyuhay/6/edit :

alert( number.length );      // 3, cause 100 has 3 digits alert( $('#demo').size()  ); // 1, use size() on elements alert( $('#demo').length );  // 1, cause 1 element #id 

• wrap code document ready function

jquery(document).ready(function( $ ) {      // dom read , ready manipulated     /* code here */ } ); 

• or place <script></script> tags before </body>