jquery: Call function by name on select change
Question
I'm trying to call a function by name .onchange of a select but nothing happens. When the function is describled after the attribute, it works.
THIS DOESN'T WORK
HTML:
<select id="numb">
<option value="1">1</option>
<option value="2">2</option>
</select>
SCRIPT:
<script type="text/javascript">
$('#numb').change(testMessage);
</script>
<script type="text/javascript">
function testMessage(){
alert('Hello');
}
</script>
THIS WORKS
HTML:
<select id="numb">
<option value="1">1</option>
<option value="2">2</option>
</select>
SCRIPT:
<script type="text/javascript">
$('#numb').change(function(){
alert('Hello')
});
</script>
EDIT:
Ok, for all those who said me to include the function on the same script. This is not possible because the testMessage() function is in an external .js script included on the <head> of the HTML.
7 answers
solution1
21 ACCPTED 2013-08-14 18:27:13
It is because the handler testMessage is not defined when binding it to the change event.
It should work if it was in the same script context like below,
<script type="text/javascript">
$('#numb').change(testMessage);
function testMessage(){
alert('Hello');
}
</script>
Code inside <script></script> are executed one by one progressive from top and testMessage function doesn't exist inside the first <script></script> .
You have couple of options here,
Put it inside an anonymous function which will let your script to resolve the
testMessagefunction later. [As suggested in Optimus Prime answer]<script type="text/javascript"> $('#numb').change(function () { testMessage }); </script> <script type="text/javascript"> function testMessage(){ alert('Hello'); } </script>Include the script that has
testMessagefunction above thescriptthat binds the testMessage like below,<script type="text/javascript"> function testMessage(){ alert('Hello'); } </script> <script type="text/javascript"> $('#numb').change(testMessage); </script>
solution2
5 2013-08-14 18:26:08
Instead try ,
<script type="text/javascript">
$('#numb').change(function(){
testMessage();
});
</script>
solution3
2 2013-08-14 18:28:17
Working Jsfiddle try this:
<script type="text/javascript">
$('#numb').on('change',testMessage);
</script>
solution4
1 2013-08-14 18:28:01
Try this and place in the same script tag:
<script type="text/javascript">
$(document).ready(function(){
$('#numb').change(testMessage);
function testMessage(){
alert('Hello');
}
});
</script>
solution5
0 2013-08-14 18:25:57
You must define a callback on the change function.
<script type="text/javascript">
$('#numb').change(function(){
testMessage();
);
function testMessage(){
alert('Hello');
}
</script>
That should fix your problem.
solution6
0 2013-08-14 18:32:32
I dont think your reference exists yet to the function here is two ways you could do it. I put the namespaced version as a suggestion because it might help clean up your code in general.
HTML:
<select id="numb">
<option value="1">1</option>
<option value="2">2</option>
</select>
SCRIPT:
// Namespaced and using Proxy
<script type="text/javascript">
var project = project || {};
project = {
testMessage: function (event) {
alert('Hello');
}
};
$('#numb').change($.proxy(project.testMessage, project));
</script>
// Just declared
<script type="text/javascript">
function testMessage(){
alert('Hello');
}
$('#numb').change(function(event) {
testMessage();
});
</script>
If your method is in another file make sure you include that file before the one with the event binding. Are you getting any console errors?
solution7
0 2021-10-05 06:04:06
you can get the value whenever you changed the value.
<select id="numb" onchange="Selecteditems()">
<option value="1">1</option>
<option value="2">2</option>
</select>
var Selecteditems = function () {
var items= $('#numb').val();
alert(items)
}
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