等候執行結果才回傳

當你需要回傳各func的執行結果

模組化後，執行的實作在提整的func中，不做額外處理(等候)會直接被當成異步，造成先傳出response沒有取得真正的執行結果。

await

azure的基本範例就是用asyns掛在func前，讓回傳自動成為異步！

與asyns搭配使用的是「await」，強迫等候處理取得結果。

module.exports = async function (context, req) {
    let responseMessage = "success";
    let status = 200;

    const action = context.bindingData.action;
    
    await (function() { 
        if(action == "action"){
            responseMessage = "處理了！";
        }
        else if(action == "ERR"){
            responseMessage = "錯誤訊息";
            status = 400;
        }
    })();

    context.res = {
        // status: 200, /* Defaults to 200 */
        status: status,
        body: responseMessage
    };
}

await後基本上是接著function，這裡用匿名函式方式處理。

不async

也可以直接放棄外層的異步。

但需要在最後呼叫「context.done();」以通知伺服器執行回傳。

然後用Promise的方法，將response的處理及context.done的呼叫當作callback傳入，在then裡執行伺服器回傳。

function search(q){
    return new Promise(function(resolve, reject) {
        ...
    });
}
    
module.exports = function (context, req) {
    context.log('JavaScript HTTP trigger function processed a request！');

    const q = (req.query.q || (req.body && req.body.q)); 

    let doResponse = function(respMsg){
        context.res = {
            // status: 200, /* Defaults to 200 */
            body: respMsg
        };
    
        context.done();
    }
    
    q ? search(q).then(doResponse) : doResponse("缺漏查詢條件！請輸入參數q值...");
}

錯誤示範！

這樣只會取得「success」（最一開始給定的值，並非執行處理後的值）。

module.exports = async function (context, req) {
    let responseMessage = "success";

    const action = context.bindingData.action;
    
    if(action == "action"){
        responseMessage = "處理了！";
    }
    else if(action == "ERR"){
        responseMessage = "錯誤訊息";
    }

    context.res = {
        body: responseMessage
    };
}

如果await的function中還有需要等待的function，外面的function也必須為async，且await目標function，否則會無效。（如下範例）

正確寫法

var search = require(`./search`);

module.exports = async function (context, req) {
    let responseMessage = "success";
    let status = 200;

    const action = context.bindingData.action;
    
    if(action == "search"){
        responseMessage = await search.search(req); //等候目標function
    }
    else if(action == "ERR"){
        responseMessage = "錯誤訊息";
        status = 400;
    }

    context.res = {
        // status: 200, /* Defaults to 200 */
        status: status,
        body: responseMessage
    };
}

無效寫法

var search = require(`./search`);

module.exports = async function (context, req) {
    let responseMessage = "success";
    let status = 200;

    const action = context.bindingData.action;
    
    await (function() { //等候目標為這個匿名func，內部的search卻沒等到
        if(action == "action"){
            responseMessage = search.search(req); //await得匿名func中無法直接再await
        }
        else if(action == "ERR"){
            responseMessage = "錯誤訊息";
            status = 400;
        }
    })();

    context.res = {
        // status: 200, /* Defaults to 200 */
        status: status,
        body: responseMessage
    };
}

search.js

async function search(req){
    let data = {};
    
    await axios.get(url)
        .then(function (response) {
            // console.log(response);
            // console.log(response.data);
            data = response.data;
        })
        .catch(function (error) {
            // console.log(error);
        })
        .then(function () {
            // always executed
        });
        
    return data;
}

exports.search = search();