AWS Lambda / Node.js函数调用序列

Question

The following piece of AWS lambda code (highly simplified):

'use strict';
var aws = require('aws-sdk');

var docClient = new aws.DynamoDB.DocumentClient();

exports.handler = (event, context, callback) => {
    var inputorder = initInputAndDbParams(event);

    queryOrders(inputorder)
        .then(findSuitableOrder.bind(null, inputorder)) //findOrder requires query result
        .then(placeNewOrder(inputorder));

    callback(null, "ORDER OK");
}

function queryOrders(inputorder) {
    return new Promise(function(resolve, reject) {
        docClient.query(inputorder.dbparams.qparams, function(err, data) {
            if (err) {
                reject(err);
            } else {
                resolve(data); // gets back the query result array
            }
        }
    }

    // Recursive!!
function findSuitableOrder(inputorder) {
    return new Promise(function(resolve, reject) {
        if (array.length === 0 || orderamount === 0) resolve();

        order = array.shift();

        if (order.article = inputorder.article) {
            deleteOrder(inputorder)
                .then(placeNewOrder);
        }
    }
}

function deleteOrder(inputorder) {
    return new Promise(function(resolve, reject) {
        docClient.delete(inputorder.dbparams.delparams, function(err, data) {
            if (err) {
                reject(err);
            } else {
                resolve(data);
            }
        }
    }

function placeNewOrder(inputorder) {
    return new Promise(function(resolve, reject) {
        docClient.put(inputorder.dbparams.wparams, function(err, data) {
            if (err) {
                reject(err);
            } else {
                resolve(data);
            }
        }
    }

function placeOrderDelivery(inputorder) {
    return new Promise(function(resolve, reject) {
        docClient.put(inputorder.dbparams.odparams, function(err, data) {
            if (err) {
                reject(err);
            } else {
                resolve(data);
            }
        });
    }
}

function initInputAndDbParams(event) {
    var inputorder = {
        article: "example",
        price: 54
        amount: 1
    };

    return inputorder;
}

The expected Order of the function calls is:

1. initInputAndDbParams
2. queryOrders
3. findSuitableOrder a) deleteOrder b) placeNewOrder
4. placeOrderDelivery

Actual result like:

1. initInputAndDbParams
2. placeOrderDelivery
3. queryOrders . .

I am using promises in all functions, except in initInputAndDbParams which returns a value. findSuitableOrder is called recursively to iterate through the array of orders.

How can I get the required sequence of function calls?

Answer 1

I got it:

queryOrders(inputorder).then(function (orders) {
    return findSuitableOrder(inputorder, orders);
}).then(function() {
    return placeNewOrder(inputorder);
}).catch(function (err) {
    console.log(err);

That works an everything is in sequence.

Thanks for all your posts and help!