Typescript中的文件头-如何等待onloadend完成以继续进程

我正在onloadend内部调用API，但无法获得响应，因为我的进程在调用完成之前继续：

async function InsertDataProjects(file3D: File, fileThumb: File, groupCod: string, projectName: string) {

    const uploadObj = async (file: File, projectName: string, objName: string, type: string) => {
        let reader = new FileReader();

        reader.readAsDataURL(file);
        reader.onloadend = async () => {
            let base64 = reader.result;
            let payload = {
                name: projectName + objName,
                type: type,
                file: base64
            }
            await s3.upload(payload).then((resp) => {
                console.log(resp);

            });
        }
}
try {
    await uploadObj(file3D, projectName, '/3d.gltf', 'base64_2');

} catch (error) {

}

我试图在reader.onloadend之前声明一个变量，并在s3.upload响应中分配它，但是 这是不可能的，因为进程在结束onloadend调用之前继续

例如：

const uploadObj = async (file: File, projectName: string, objName: string, type: string) => {
    let reader = new FileReader();

    let response: any;
    reader.readAsDataURL(file);
    reader.onloadend = async () => {
        let base64 = reader.result;
        let payload = {
            name: projectName + objName,
            type: type,
            file: base64
        }
        await s3.upload(payload).then((resp) => {
            response = resp;
        });
    }

    return response;
}

我还尝试在onloadend之后调用API，但也出现了错误，因为我的有效负载未定义。 例如：

如何将s3.upload的响应返回到InsertDataProjects

let resp = await uploadObj(file3D, projectName, '/3d.gltf', 'base64_2');

let resp = await uploadObj(file3D, projectName, '/3d.gltf', 'base64_2');