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for loop async in node js

Hi I have a for loop in my node js application which calls an async function. I want to check a value and decide whether a customer is found or not. But the loop iterates until the last element. Hence my error loop is not working. I want the loop to check the response and then iterate the next loop.
for loop:
for (let i = 0; i < customerlookupresponse.data.length; i++) {
var customer = customerlookupresponse.data[i];
if (customer != undefined) {
console.log("customer.id :: " + customer.id)
var accountlookUpData = {
customerId: customer.id
};
customerAccountLookUpRequest(accountlookUpData).then(data => {
console.log("----" + i + " -- " + data);
if (data && data.status === 1) {
resolve(data);
return;
}else{
reject({
status: 404,
message: "Customer not found"
});
return;
}
});
} else {
reject({
status: 404,
message: "Customer not found"
});
return;
}
}
the async function:
async function customerAccountLookUpRequest(customerLookUpData) {
var accountLookUp = config.app.url;
let data = await axios.get(accountLookUp).then(accountLookUpResult => {
for (i = 0; i < accountLookUpResult.data.length; i++) {
var requestaccount = accountLookUpResult.data[i].accountNumber;
if (requestaccount == customerLookUpData.lookupAccount) {
accountLookUpResult.data[i].customerId = customerLookUpData.customerId;
accountLookUpResult.data[i].status = 1;
return accountLookUpResult.data[i];
}
}
});
return data;
}
I am new to node js and trying to understand the concept of async await. Please help.

An async function waits for a Promise to return. The function that has the loop should be declared as async and the customerAccountLookUpRequest function should return a promise. Then use the await operator to call the function. Simple example:
class some_class {
constructor() {
}
async my_loop() {
let _self = this;
for (let i = 0; i < customerlookupresponse.data.length; i++) {
let data = await _self.customerAccountLookUpRequest(accountlookUpData);
console.log("----" + i + " -- " + data);
}
}
customerAccountLookUpRequest(customerLookUpData) {
return new Promise((resolve, reject) => {
axios.get(accountLookUp).then(accountLookUpResult => {
resolve(accountLookUpResult);
});
});
}
}

How to make a JavaScript class or function that will make the following code work? I can't use promise and await

Here is what should be output to console:
1 hello
2 a
3 b
And here is the code for which i should make a class or a function:
var d = new deferred();
d.then(function(res) {
console.log("1 ", res);
var d1 = new deferred();
setTimeout(function() {
d1.resolve("a");
}, 150);
return d1;
});
d.then(function(res) {
console.log("2 ", res);
return "b";
});
d.then(function(res) {
console.log("3 ", res);
return "c";
});
d.resolve("hello");
I should create a class or a
function with name "deferred"
I've already done almost everything except i can't make it get the result from setTimeout
function.
function deferred() {
this.arrfunc = [];
this.buffstr = null;
this.bufffunc;
this.result;
this.then = function(callback) {
this.arrfunc.push(callback);
}
this.wait = function() {
while (this.buffstr == null) {}
return this.buffstr;
}
this.resolve = function(str) {
this.buffstr = str;
while (this.arrfunc.length != 0) {
//console.log(typeof(this.buffstr));
if (typeof(this.buffstr) === "object") {
this.buffstr = this.buffstr.wait();
}
this.bufffunc = this.arrfunc.shift();
this.buffstr = this.bufffunc(this.buffstr);
}
}
}
The main problem in my implemenetation that its somehow stuck in while loop. And don't want to get a result after setTimeout expired.

It seems like maybe you are making this too complicated with all the different state properties. If these are you only requirements, you really only need a queue of callbacks to hold on to all the functions passed into then(). Like regular promises you need to act differently depending on whether the callback returns a regular value or another deferred instance.
function deferred() {
this.callbacks = []
}
deferred.prototype.then = function(cb) {
this.callbacks.push(cb)
}
deferred.prototype.resolve = function(val) {
let f = this.callbacks.shift()
if (f) {
let n = f(val)
if (n instanceof deferred) n.then((v) => this.resolve(v))
else this.resolve(n)
}
}
var d = new deferred("one");
d.then(function(res) {
console.log("1 ", res);
var d1 = new deferred("two");
setTimeout(function() {
d1.resolve("a");
}, 550);
return d1;
});
d.then(function(res) {
console.log("2 ", res);
return "b";
});
d.then(function(res) {
console.log("3 ", res);
return "c";
});
d.resolve("hello")

ReplaceAll causing issues in array.reduce

I am still pretty new to this, so forgive me if I dont' say this correctly. We have an array.reduce that calls a method with a returning promise that iterates through a list of files and post results to the db. Everything was working great, until it ran into a field that had an apostrophe in it and then the db insert fails. This is the field value. 'Expected 100002822' to be 100002822.'
I tried adding a replaceAll on the field and now get an error in the array.reduce.
Here is the .reduce
console.log('Found test results in ' + matches.length + ' files. Parsing and posting to the database now...');
var startTime = moment();
var parser = new Parser();
matches.reduce(function (p, val) {
return p.then(function () {
return parser.parseResults(val);
});
}, Promise.resolve()).then(function (finalResult) {
var endTime = moment();
var testDuration = moment.duration(endTime.diff(startTime));
console.log(chalk.blue('*** File parsing time: ' + testDuration.humanize() + ' ***'));
if (finalResult.insertSuccess == matches.length) {
var publishOut = {
totalFiles: matches.length,
totalTests: 0,
totalTestsSuccess: 0,
totalTestsFailed: 0
}
publishOut.totalTests += finalResult.totalTests;
publishOut.totalTestsSuccess += finalResult.testPassedCount;
publishOut.totalTestsFailed += finalResult.testFailedCount;
console.log(`Successfully inserted ${finalResult.insertSuccess} of ${publishOut.totalTests} test results.`);
// for (var i = 0; i < matches.length; i++) {
// var currentFile = `./testing/results/${matches[i]}`;
// fs.unlinkSync(currentFile);
// }
resolve(publishOut);
} else {
reject('Only ' + finalResult.insertSuccess + ' of ' + matches.length + ' successfully posted to the database');
}
}, function (err) {
reject('error in reduce', err);
});
I have tried several different ways of using the replaceAll with the same failure. It hits this code from the array.reduce
}, function (err) {
reject('error in reduce', err);
});
And this is the called method. The added code causing the failure in the .reduce is this Message = expectation.message.replaceAll("'", "");
protractorParser.prototype.parseResults = function (fileName) {
return new Promise((resolve, reject) => {
//console.log('In parseresults', fileName);
var currentFile = './testing/results/' + fileName
json.readFile(currentFile, function (err, obj) {
if (err != null) {
console.log('error reading file', err);
reject(err);
} else {
resolve(obj);
}
});
}).then(function (obj) {
var results = [];
for (var suite in obj) {
var specs = obj[suite].specs;
for (let i = 0; i < specs.length; i++) {
const assert = specs[i];
const tcR = /TC[\d]+/;
const tc = assert.description.match(tcR);
let Passed = 1;
let Message = '';
let Stack = '';
testResults.totalTests++;
if (assert.failedExpectations.length) {
const expectation = assert.failedExpectations[assert.failedExpectations.length - 1];
Passed = 0;
Message = expectation.message.replaceAll("'", "");
Stack = expectation.stack.split('\n')[1].trim();
testResults.testFailedCount++
} else {
testResults.testPassedCount++
}
if (tc != null) {
const time = moment().utcOffset(config.get('settings.timeOffset')).format('YYYY-MM-DDTHH:mm:ss');
const promise = utility.TestDataManager.insertAutomationResults(tc[0], assert.description, Passed, process.env.testBuild, 'P', Message, Stack, 0, time, '');
results.push(promise.then(() => {
//fs.unlinkSync(currentFile);
testResults.insertSuccess++;
//console.log('insertSuccess', testResults.insertSuccess);
},
err => { console.log('… failed', err); throw err; }
));
} else {
console.log('no test case found for test: ' + assert.description + ' -- skipping');
// I don't think you want to `throw err` here, right?
}
}
}
return Promise.all(results).then(() => testResults);
});
};

Foreach with Promise not waiting on method results

I am trying to iterate through the JSON files generated by the protractor tests. I pull all the file names into an array and call a method that opens and parses through the each file, post the results to the database and pass back a passed/failed flag.
I have tried all the examples here
Make angular.forEach wait for promise after going to next object and still get the same results.
The method is actually called, but the results are not posted to the db. I have tested the parser.parseResults on an individual file and it successfully posted to the db, so it has to have something to do with the promise not resolving correctly.
Is it not possible to do something like this in the jasmine/protractor framework? Or do I have something wrong in the code?
I have included the code for my latest attempt.
Thank You
Christine
matches.reduce(function (p, val) {
console.log('val', val);
return p.then(function () {
return parser.parseResults(val);
});
}, Promise.resolve()).then(function (finalResult) {
console.log('finalResult = ', finalResult);
}, function (err) {
console.log('error in reduce',err);
});
parser.parseResults code
protractorParser.prototype.parseResults = function (fileName) {
return new Promise((resolve, reject) => {
console.log('In parseresults', fileName);
json.readFile(fileName, function (err, obj) {
try {
if (err != null) {
console.log('error reading file',err);
reject(err);
}
console.log('obj - ',obj);
var results = [];
var Passed = 0;
var Message = '';
var Stack = '';
for (var suite in obj) {
var specs = obj[suite].specs;
console.log('spec - ', specs);
if (specs.length > 0) {
for (var i = 0; i < specs.length; i++) {
var assert = specs[i];
var tcR = new RegExp(/TC[\d]+/);
var tc = assert.description.match(tcR);
if (!assert.failedExpectations.length) {
Passed = 1;
}
else {
assert.failedExpectations.forEach((expectation) => {
Message = expectation.message;
Stack = expectation.stack.split('\n')[1].trim();
})
Passed = 0;
}
if (tc != null) {
utility.TestDataManager.insertAutomationResults(tc[0], assert.description, Passed, process.env.testBuild,
'P', Message, Stack, 0, moment().utcOffset(config.get('settings.timeOffset')).format('YYYY-MM-DDTHH:mm:ss'), '')
.then(function (resp) {
resolve(Passed);
}, (err) => {
console.log('Posting to Database failed ', err);
reject(err);
});
} else {
console.log('no test case found for test: ' + assert.description + ' -- skipping');
reject(err);
}
}
}
}
}
catch (err) {
console.log('rejecting opening file');
reject(err);
}
});
})
}

If there is not exactly one suite in the obj, with exactly one spec, then your promise is either resolved not at all or multiple times.
Avoid wrapping too many things in the new Promise constructor - always promisify on the smallest possible level, and use promise chaining afterwards.
protractorParser.prototype.parseResults = function (fileName) {
return new Promise((resolve, reject) => {
console.log('In parseresults', fileName);
json.readFile(fileName, function (err, obj) {
if (err != null) {
console.log('error reading file', err);
reject(err);
} else {
resolve(obj);
}
});
}).then(function(obj) {
console.log('obj - ',obj);
var results = [];
for (var suite in obj) {
var specs = obj[suite].specs;
console.log('spec - ', specs);
for (let i = 0; i < specs.length; i++) {
const assert = specs[i];
const tcR = /TC[\d]+/;
const tc = assert.description.match(tcR);
let Passed = 1;
let Message = '';
let Stack = '';
if (assert.failedExpectations.length) {
const expectation = assert.failedExpectations[assert.failedExpectations.length-1];
Passed = 0;
Message = expectation.message;
Stack = expectation.stack.split('\n')[1].trim();
}
if (tc != null) {
const time = moment().utcOffset(config.get('settings.timeOffset')).format('YYYY-MM-DDTHH:mm:ss');
const promise = utility.TestDataManager.insertAutomationResults(tc[0], assert.description, Passed, process.env.testBuild, 'P', Message, Stack, 0, time, '');
results.push(promise.catch(err => {
console.log('Posting to Database failed ', err);
throw err;
}));
} else {
console.log('no test case found for test: ' + assert.description + ' -- skipping');
// I don't think you want to `throw err` here, right?
}
}
}
return Promise.all(results);
});
};

Node.js Function Flow

When I get a request, I want it to generate a 4-character code, then check if it already exists in the database. If it does, then generate a new code. If not, add it and move on. This is what I have so far:
var code = "";
var codeFree = false;
while (! codeFree) {
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var code = "";
for (var i = 0; i < 4; i++) {
var rand = Math.floor(Math.random() * chars.length);
console.log(rand);
code += chars.charAt(rand);
}
console.log("Code: %s generated.", code);
client.execute("select * from codes where code=" + code, function(err, result) {
if (! err) {
if (result.rows.length > 0) {
codeFree = false;
} else {
codeFree = true;
}
} else {
console.log('DB ERR: %s', err);
}
console.log(codeFree);
});
console.log('here');
}
This does not do nearly what I want it to do. How can I handle something like this?

You are doing an async task.
When you have an asyncronous task inside your procedure, you need to have a callback function which is going to be called with the desired value as its argument.
When you found the free code, you call the function and passing the code as its argument, otherwise, you call the getFreeCode function again and passing the same callback to it. Although you might consider cases when an error happens. If your the db call fails, your callback would never get called. It is better to use a throw/catch mechanism or passing another argument for error to your callback.
You can achieve what you need to do by doing it this way:
function getFreeCode(callback) {
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var code = "";
for (var i = 0; i < 4; i++) {
var rand = Math.floor(Math.random() * chars.length);
console.log(rand);
code += chars.charAt(rand);
}
console.log("Code: %s generated.", code);
client.execute("select * from codes where code="+code, function(err, result) {
if(!err) {
if(result.rows.length > 0) {
getFreeCode(callback);
} else {
callback(code);
}
}else {
console.log('DB ERR: %s', err);
}
console.log(codeFree);
});
console.log('here');
}
// in your main:
getFreeCode(function (code) {
console.log(' this code was free: ' + code)
})

I recommend you look into two alternatives to help deal with asynchronous code.
node generator functions using the 'yield' keyword
promises
Using generators requires running a recent version of node with the --harmony flag. The reason I recommend generators is because you can write code that flows the way you expect.
var x = yield asyncFunction();
console.log('x = ' + x);
The previous code will get the value of x before logging x.
Without yielding the console.log would write out x before the async function was finished getting the value for x.
Your code could look like this with generators:
var client = {
execute: function (query) {
var timesRan = 0;
var result = [];
return function () {
return setTimeout(function () {
result = ++timesRan < 4 ? ['length_will_be_1'] : [];
return result;
},1);
};
}
};
function* checkCode () {
var code;
var codeFree = false;
while(!codeFree) {
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
code = "";
for (var i = 0; i < 4; i++) {
var rand = Math.floor(Math.random() * chars.length);
console.log(rand);
code += chars.charAt(rand);
}
console.log("Code: %s generated.", code);
try {
var result = yield client.execute("select * from codes where code="+code);
codeFree = result.rows.length > 0 ? false : true;
}catch(e) {
console.log('DB ERR: %s', err);
} finally {
console.log(codeFree);
}
console.log('here');
}
}
checkCode().next();
You would leave off the client object. I only added that to make a working example that fakes an async call.
If you have to use an older version of node or do not like the yield syntax then promises could be a worthy option.
There are many promise libraries. The reason I recommend promises is that you can write code that flows the way you expect:
asyncGetX()
.then(function (x) {
console.log('x: ' + x);
});
The previous code will get the value of x before logging x.
It also lets you chain async functions and runs them in order:
asyncFunction1()
.then(function (result) {
return asyncFunction2(result)
})
.then(function (x) { /* <-- x is the return value from asyncFunction2 which used the result value of asyncFunction1 */
console.log('x: ' + x);
});
Your code could look like this with the 'q' promise library:
var Q = require('q');
var client = {
timesRan: 0,
execute: function (query, callback) {
var self = this;
var result = {};
setTimeout(function () {
console.log('self.timesRan: ' + self.timesRan);
result.rows = ++self.timesRan < 4 ? ['length = 1'] : [];
callback(null, result);
},1);
}
};
function checkCode () {
var deferred = Q.defer();
var codeFree = false;
var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
var code = "";
for (var i = 0; i < 4; i++) {
var rand = Math.floor(Math.random() * chars.length);
console.log('rand: %s', rand);
code += chars.charAt(rand);
}
console.log("Code: %s generated.", code);
client.execute("select * from codes where code="+code, function(err, result) {
console.log('err: '+err+', result: ' + JSON.stringify(result));
console.log('result.rows.length: ' + result.rows.length);
if(!err) {
if(result.rows.length > 0) {
codeFree = false;
console.log('result.rows: %s, codeFree: %s', result.rows, codeFree);
checkCode();
} else {
codeFree = true;
console.log('line 36: codeFree: ' + codeFree);
deferred.resolve(code);
}
}else {
console.log('DB ERR: %s', err);
deferred.reject(err);
}
console.log(codeFree);
});
console.log('waiting for promise');
return deferred.promise;
}
checkCode()
.then(function (code) {
console.log('success with code: ' + code);
})
.fail(function(err) {
console.log('failure, err: ' + err);
});
Also omit the client object here. I only added that to make a working example that fakes an async call.
Promises and generators definitely take some time to get used to. It's worth it because they make the code a lot easier to follow in the end than code written with nested callbacks.