[英]Run one function after another in javascript
I am using javascript to use the facebook send api. 我正在使用JavaScript使用Facebook发送API。
function sendmessage(callback) {
for (i = 0; i < recipientId.length; i++) {
var messageData = {
recipient: {
id: recipientId[i]
},
message: {
text: messageText
}
};
callSendAPI(messageData, pagetoken, id_notsent);
}
return callback( );
}
function sendstatus() {
if (id_notsent.length == 0) {
res.statusCode = 200;
res.message = "Successfully sent generic message to all recipients";
} else {
res.statusCode = 400;
res.message = "Unable to send message to all users. Message not sent to recipients : " + id_notsent.toString();
};
resp.send(res);
}
sendmessage(sendstatus);
What i am trying to do is to update the id_notsent variable inside the sendmessage function which will basically contain user id correspoding to which message couldn't be send and then sending back the response accordingly using sendstatus function. 我正在尝试做的是更新sendmessage函数中的id_notsent变量,该变量将基本上包含对应于无法发送消息的用户ID,然后使用sendstatus函数相应地将响应发送回去。 but the problem is that the callback in sendmessage is getting called before the callSendAPI function is completed. 但问题是在callSendAPI函数完成之前已调用sendmessage中的回调。
You have multiple soluce here : 您在这里有多种解决方案:
Using async/await
ES8 pattern. 使用async/await
ES8模式。
function async sendmessage() {
for (i = 0; i < recipientId.length; i++) {
var messageData = { ... };
await callSendAPI(messageData, pagetoken, id_notsent);
}
return ...;
}
Create a recursive function that's gonna call one by one the callSendAPI
. 创建一个递归函数,该函数将一次调用callSendAPI
。
For example : 例如 :
function sendmessage({
recipientId,
callback,
i = 0,
rets = [],
}) {
// our work is done
if (i >= recipientId.length) return callback(rets);
const messageData = { ... };
// Perform one request
callSendAPI(messageData, pagetoken, id_notsent, (ret) => {
// Call next
return sendmessage({
recipientId,
callback,
rets: [
...rets,
ret,
],
i: i + 1,
});
});
}
You can use either callback
(what you are doing now), or either Promise
. 您可以使用callback
(您现在正在做什么)或Promise
。
I suspect callSendAPI
is return some sort of Promise
(or has a callback that you can turn into a Promise). 我怀疑callSendAPI
返回某种形式的Promise
(或具有一个可以转变为Promise的回调)。
The structure your sendMessage()
function should then be around the lines of 然后, sendMessage()
函数的结构应与
const promises = recipentId.map( id => {
...
return callSendAPI(messageData, pagetoken, id_notsent);
});
Promise.all(promises).then(callback);
Basically: get promises for all your calls, wait for them to complete using Promise.all
then callback 基本上:为您的所有呼叫获得承诺,使用Promise.all
等待它们完成,然后回调
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