从查询返回的文档中添加字段到子文档

Question

我想在返回的子文档中添加一个字段，如下所示：

// Get a reference to the image element
var elephant = document.getElementById("elephant");

// Take action when the image has loaded
elephant.addEventListener("load", function () {
    var imgCanvas = document.createElement("canvas"),
        imgContext = imgCanvas.getContext("2d");

    // Make sure canvas is as big as the picture
    imgCanvas.width = elephant.width;
    imgCanvas.height = elephant.height;

    // Draw image into canvas element
    imgContext.drawImage(elephant, 0, 0, elephant.width, elephant.height);

    // Get canvas contents as a data URL
    var imgAsDataURL = imgCanvas.toDataURL("image/png");

    // Save image into localStorage
    try {
        localStorage.setItem("elephant", imgAsDataURL);
    }
    catch (e) {
        console.log("Storage failed: " + e);
    }
}, false);

我可以通过{ "type": "product", "code": "abc", "team": "A1", "modules": [{ "type": "module", "code": "cde" //Add a new field here }] } 在文档中添加新字段，但无法添加到子文档中。

这是我的Java代码：

Document.append()

有人可以帮忙吗？非常感谢提前!!!