//create an object to act as a namespace
var sharePoint = {};
//Function that makes the client side call to the server
sharePoint.getListItem = function (id, listName, onSuccess, onFailure) {
    sharePoint.clientContext = SP.ClientContext.get_current();
    sharePoint.list = sharePoint.clientContext.get_web().get_lists().getByTitle(listName);
    sharePoint.listItem = sharePoint.list.getItemById(id);
    sharePoint.clientContext.load(sharePoint.listItem);
    sharePoint.clientContext.load(sharePoint.listItem.get_attachmentFiles());
    sharePoint.clientContext.executeQueryAsync(Function.createDelegate(this, onSuccess), Function.createDelegate(this, onFailure));
};
//If successful, this method is called
sharePoint.onSuccess = function (sender, args) {
    var item = sharePoint.listItem;
    var total = item.get_attachmentFiles().get_count();
    if (total > 0) {
        console.log("I found " + total + " file attachments");
    }
    for (var count = 0; count < total; count++) {
        var spfile = item.get_attachmentFiles().get_item(count);
        var fileName = spfile.get_fileName();
        var serverRelativeUrl = spfile.get_serverRelativeUrl();
        console.log("Filename: " + fileName + " File Path: " + serverRelativeUrl);
    }
    /* Example output:
    
    I found 1 file attachments 
    Filename: Sample.jpg File Path: /subsite/Lists/MyList/Attachments/58/Sample.jpg 
    */
};
//If an error occurs this method is called
sharePoint.onFailure = function (sender, args) {
    if (args instanceof SP.ClientRequestFailedEventArgs) {
        var message = args.get_message();
        var code = args.get_errorCode();
        var details = args.get_errorDetails();
        var value = args.get_errorValue();
        var typeName = args.get_errorTypeName();
        var stack = args.get_stackTrace();
        var correlationId = args.get_errorTraceCorrelationId();
        alert('Error: ' + message + ".");
    } else {
        alert('Unexpected Error');
    }
};
//This method initates the process
function Test() {
    sharePoint.getListItem("58", "MyList", sharePoint.onSuccess, sharePoint.onFailure);
}
$(document).ready(function () {
    ExecuteOrDelayUntilScriptLoaded(Test, "SP.js");
});