GetElementsByTagName not working in chrome and safari

Question

I use the javascript getElementsByTagName ("a") method to call all the "a" tags and the effect with them. This method works in FF and Opera, but not in Chrome and Safari. When I look in the debugging tools of Chrome and Safari, they say: "Do not dig TypeError: cannot call the method" getElementsByTagName "from null"

Why is this and what is the fix? Can someone advise me on this?

Thank you very much in advance.

Here is the code:

function popUpSAPWindow(){
// Find all links in the page and put them into an array.
var linksInOrderLinesTable = document.getElementById("orderLinesTable").getElementsByTagName("a"); // The line doing the error
var linksLen = linksInOrderLinesTable.length;

// If the link text is 'SAP' then modify the attributes
for(var i = 0; i < linksLen; i++){
    if(linksInOrderLinesTable[i].innerHTML == "SAP"){
        // Store the 'href' value of each SAP link.
        var sapHref = linksInOrderLinesTable[i].href;

        // Modify the attributes of each SAP link.      
        linksInOrderLinesTable[i].setAttribute("href", "javascript:return false;");
        linksInOrderLinesTable[i].setAttribute("onclick", "sapNewWindow(\'" + sapHref + "\')");
    }
}

}

It works with this HTML:

<table id="orderLinesTable" summary="List of orders made by customers that the administrator can pick and deal with">
<tr>
    <th>Status</th>
    <th>Basket id</th>
    <th>Order line id</th>
    <th>Product</th>
    <th>Company</th>
    <th>Catalogue</th>
    <th>Date</th>
    <th>Details</th>
</tr>
<tr>
    <td>Accepted</td>
    <td>236569</td>
    <td>207</td>
    <td>OS Master Map</td>
    <td>NHS</td>
    <td>Standard</td>
    <td>1 Aug 10</td>
    <td><a href="/orderLineDetails.html">Normal</a> <a href="/orderLineDetails.html">SAP</a></td>
</tr>
<tr>
    <td>New</td>
    <td>236987</td>
    <td>528</td>
    <td>Code-Point</td>
    <td>BT</td>
    <td>Standard</td>
    <td>9 Aug 10</td>
    <td><a href="/orderLineDetails.html">Normal</a> <a href="/orderLineDetails.html">SAP</a></td>
</tr>

But when I'm on other pages, this indicates an error.

Answer 1

, document.getElementById("orderLinesTable").getElementsByTagName("a") , orderLinesTable, getElementById null. getElementsByTagName null .

:

var orderLinesTable = document.getElementById("orderLinesTable");
var linksInOrderLinesTable = [];

if (orderLinesTable) { // only get the links when the table exists
    linksInOrderLinesTable = orderLinesTable.getElementsByTagName("a");
}

Answer 2

Safari Chrome . , , , null. , , .

: Javascript, DOM API.

EDIT:

document.getElementById("orderLinesTable")

, . ?