eBay API find items by keyword using Javascript returns 'Uncaught TypeError'

Question

I am a beginner programmer and I am trying to find items for my hybrid mobile application from eBay with specific keywords using their Finding API through Javascript.

I followed this really clear guide, but I am not getting anything to appear in my results div. I have also tried running the exact code on a website, but still no results. I have also acquired and entered the correct production appID in the field.

Here are the codes:

<script>                    
    var url = "http://svcs.ebay.com/services/search/FindingService/v1";
    url += "?OPERATION-NAME=findItemsByKeywords";
    url += "&SERVICE-VERSION=1.0.0";
    url += "&SECURITY-APPNAME=sample-sample-PRD-89a6113e8-f7a52044";
    url += "&GLOBAL-ID=EBAY-US";
    url += "&RESPONSE-DATA-FORMAT=JSON";
    url += "&callback=_cb_findItemsByKeywords";
    url += "&REST-PAYLOAD";
    url += "&keywords=harry%20potter";
    url += "&paginationInput.entriesPerPage=3";
    url += urlfilter;
    alert(url);
    // Submit the request
    s = document.createElement('script'); // create script element
    s.src = url;

    // Error received on the line below, "uncaught typeerror: cannot call method 'appendChild' of null"
    document.body.appendChild(s);

    function _cb_findItemsByKeywords(root) {
        var items = root.findItemsByKeywordsResponse[0].searchResult[0].item || [];
        var html = [];
        html.push('<table width="100%" border="0" cellspacing="0" cellpadding="3"><tbody>');
        for (var i = 0; i < items.length; ++i) {
            var item = items[i];
            var title = item.title;
            var pic = item.galleryURL;
            var viewitem = item.viewItemURL;
            if (null != title && null != viewitem) {
                html.push('<tr><td>' + '<img src="' + pic + '" border="0">' + '</td>' +
                    '<td><a href="' + viewitem + '" target="_blank">' + title + '</a></td></tr>');
            }
        }
        html.push('</tbody></table>');
        document.getElementById("results").innerHTML = html.join("");
    } // End _cb_findItemsByKeywords() function

    // Create a JavaScript array of the item filters you want to use in your request
    var filterarray = [{
            "name": "MaxPrice",
            "value": "25",
            "paramName": "Currency",
            "paramValue": "USD"
        },
        {
            "name": "FreeShippingOnly",
            "value": "true",
            "paramName": "",
            "paramValue": ""
        },
        {
            "name": "ListingType",
            "value": ["AuctionWithBIN", "FixedPrice"],
            "paramName": "",
            "paramValue": ""
        },
    ];

    // Define global variable for the URL filter
    var urlfilter = "";

    // Generates an indexed URL snippet from the array of item filters
    function buildURLArray() {
        alert("buildURLArray working");
        // Iterate through each filter in the array
        for (var i = 0; i < filterarray.length; i++) {
            //Index each item filter in filterarray
            var itemfilter = filterarray[i];
            // Iterate through each parameter in each item filter
            for (var index in itemfilter) {
                // Check to see if the paramter has a value (some don't)
                if (itemfilter[index] !== "") {
                    if (itemfilter[index] instanceof Array) {
                        for (var r = 0; r < itemfilter[index].length; r++) {
                            var value = itemfilter[index][r];
                            urlfilter += "&itemFilter\(" + i + "\)." + index + "\(" + r + "\)=" + value;
                        }
                    } else {
                        urlfilter += "&itemFilter\(" + i + "\)." + index + "=" + itemfilter[index];
                    }
                }
            }
        }
    } // End buildURLArray() function

    // Execute the function to build the URL filter
    buildURLArray(filterarray);
</script>

HTML:

<h1>eBay Search Results</h1>
<div id="results"></div>

There are two alerts:

1. alert(url) returned everything, except for urlfilter being undefined
2. alert("buildURLArray working"); did not appear.

Eclipse returned an error for line document.body.appendChild(s);, suggesting that it is null.

Uncaught TypeError: cannot call method 'appendChild' of null

Most of the codes are from the tutorial and I have no idea why I am not getting the same results.

Answer 1

In URL construction code , urlFilter isn't defined because of the sequential nature of interpreter ; assignments aren't hoisted ie in simple words you can't use its future value in the present. so just cut the code beginning from var URL= ... (1st line ) till document.body.appendChild(s); and paste it at the end (after buildURLArray(filterarray);) inside your script tag.Now urlFilter will get some value and after that will be used in URL construction.