duanan5940 2015-10-06 02:11
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由于某种原因，document.getElementById（）。innerHTML不起作用？

i have a span with the same value..

echo "<span id='msgNotif1' class='badge'  style='position:relative;right:5px;bottom:10px;'>".$number."</span>";

where $number have a value..

and my js code is..

var xmlhttp = new XMLHttpRequest();
        xmlhttp.onreadystatechange = function() {
            if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                var val = xmlhttp.responseText;
                //alert(val);
                document.getElementById("msgNotif1").innerHTML = val;
                //document.getElementById("msgNotif2").innerHTML = val;
                alert(val);
                //document.getElementById("msgNotif3").innerHTML = xmlhttp.responseText;    
            }
        }
        xmlhttp.open("GET", "some page", true);
        xmlhttp.send();

the problem is the value still remains and do not change, trying to uncomment the first alert shows an alert with the right value, but when i try to comment it the second alert never executed, giving me an idea that the document.getelementbyid().innerhtml is the one that is not working, been with this for a few hours, any help will be appreciated. thanks in advance

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  • drap5081683 2015-10-06 02:19
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    Your error message Cannot set property 'innerHTML' of null" means that:

    document.getElementById("msgNotif1")

    is returning null. That can happen for several possible reasons:

    1. There is no element in your page with id="msgNotif1".
    2. You are calling this code before your document has finished loading and thus the element with id="msgNotif1" has not yet loaded. This can commonly happen if you execute your code in the <head> section of the document rather than at the very end of <body> or in response to the DOMContentLoaded event.
    3. Your content is dynamically loaded (not in the original page HTML) and you are calling document.getElementById("msgNotif1") before your dynamic content has been loaded.
    4. You have some HTML errors which are preventing the proper parsing of your HTML that contains the element with id="msgNotif1".

    For a general purpose description of how to run Javascript after the current page has been loaded without using a framework like jQuery, see this answer: pure JavaScript equivalent to jQuery's $.ready() how to call a function when the page/dom is ready for it

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