Javascript in the Onload Event for a SharePoint Page

The simple way to add JavaScript behaviours to a SharePoint page is to add a script block with the for and event attributes set to the relevant object and event.

For instance, to insert a value from the querystring into the page title, add the following script to the top of the PlaceHolderMain Content Place Holder block:

    <script type="text/javascript" language="javascript">
    function getQueryStringValue(qsName) {
        var querystring = window.location.search.substring(1);
        var qsPair = querystring.split("&");
        for (var i=0;i<qsPair.length;i++) {
            var pair = qsPair[i].split("=");
            if (pair[0].toLowerCase() == qsName.toLowerCase()) {
                  return pair[1];
            }
        } 
        return '';
    }    
    </script>
    <script type="text/javascript" language="javascript" for="window" event="onload">
        document.title = 'Details for ' + getQueryStringValue('supplier') + document.title;
    </script>