Node.js : Call function using value from callback or async - node.js

Question

I have written below .js file to call below defined function.
objectRepositoryLoader.readObjectRepository() returns me a hashmap from where i have to use values in enterUserName(), enterPassword(), clickLoginButton() functions.
var path = require('path');
var elementRepoMap = {}
var LandingPage = function(){
var fileName = path.basename(module.filename, path.extname(module.filename))
objectRepositoryLoader.readObjectRepository(fileName+'.xml' , function(elementRepo){
console.log(elementRepo) //values are being printed here
this.elementRepoMap = elementRepo
});
this.enterUserName = function(value){
console.log(elementRepoMap) //values are not being printed here
//Some Code
};
this.enterPassword = function(value){
//Some Code
};
this.clickLoginButton = function(){
//Some Code
};
};
module.exports = new LandingPage();
The objectRepositoryLoader.readObjectRepository() function defined in another file is as below:
var ObjectRepositoryLoader = function() {
this.readObjectRepository = function(fileName, callback) {
var filePath = './elementRepository/'+fileName;
this.loadedMap = this.objectRepoLoader(filePath, function(loadedMap){
return callback(loadedMap);
});
}
this.objectRepoLoader = function(filePath, callback){
if (filePath.includes(".xml")) {
this.xmlObjectRepositoryLoader(filePath, function(loadedMap){
return callback(loadedMap);
});
}
this.xmlObjectRepositoryLoader = function (xmlPath, callback){
var innerMap = {};
var elementName;
fs.readFile(xmlPath, "utf-8",function(err, data) {
if(err){
console.log('File not found!!')
}
else{
var doc = domparser.parseFromString(data,"text/xml");
var elements = doc.getElementsByTagName("A1");
for(var i =0 ; i< elements.length;i++){
var elm = elements[i];
elementName = elm.getAttribute("name");
var params = elm.getElementsByTagName("AS");
innerMap = {};
for(var j =0 ; j< params.length;j++){
var param = params[j];
var locatorType = param.getAttribute("type");
var locatorValue = param.getAttribute("value");
innerMap[locatorType] = locatorValue;
}
loadedMap[elementName] = innerMap;
innerMap={};
};
}
return callback(loadedMap);
});
};
How can I call enterUserName(), enterPassword(), clickLoginButton() function from spec.js file and is there any way I can avoid using callback and use async.js and call enterUserName(), enterPassword(), clickLoginButton() from spec.js file ?
EDIT
I have modified my file like below:
this.xmlObjectRepositoryLoader = function (xmlPath){
var innerMap = {};
var elementName;
var filePath = xmlPath+'.xml'
var self = this
return new Promise(
function(resolve, reject){
console.log("In xmlObjectRepositoryLoader : "+filePath)
self.readFilePromisified(filePath)
.then(text => {
var doc = domparser.parseFromString(text,"text/xml");
var elements = doc.getElementsByTagName("Element");
for(var i =0 ; i< elements.length;i++){
var elm = elements[i];
elementName = elm.getAttribute("name");
var params = elm.getElementsByTagName("param");
innerMap = {};
for(var j =0 ; j< params.length;j++){
var param = params[j];
var locatorType = param.getAttribute("type");
var locatorValue = param.getAttribute("value");
innerMap[locatorType] = locatorValue;
}
map[elementName] = innerMap;
innerMap={};
}
console.log(map) // prints the map
resolve(text)
})
.catch(error => {
reject(error)
});
});
}
this.readFilePromisified = function(filename) {
console.log("In readFilePromisified : "+filename)
return new Promise(
function (resolve, reject) {
fs.readFile(filename, { encoding: 'utf8' },
(error, data) => {
if (error) {
reject(error);
} else {
resolve(data);
}
})
})
}
I am calling above function from another file as below:
objectRepositoryLoader.readObjectRepository(fileName)
.then(text => {
console.log(text);
})
.catch(error => {
console.log(error);
});
But it gives me error as
.then(text => { ^
TypeError: Cannot read property 'then' of undefined
In this case how can I use promise to call another promise function and then use the returned value in one more promise function and return calculated value to calling function where I can use the value in other functions. I sound a bit confused. Please help

Answer 1

You can use async.waterfall and async.parallel to perform this task
see the reference
I just tried your code to make it working, I explained the way of implementation in comment.
async.waterfall([
function(next){
objectRepositoryLoader.readObjectRepository(fileName+'.xml' ,next)//pass this next as parameter in this function defination and after manipulation return result with callback like this(null,result)
}
],function(err,result){
if(!err){
//Do wahtever you want with result
async.parallel([
function(callback){
this.enterUserName = function(value){
console.log(elementRepoMap)
//Some Code
};
},
function(callback){
this.enterPassword = function(value){
//Some Code
};
},
function(callback){
this.clickLoginButton = function(){
//Some Code
};
}
], function(err, results) {
// optional callback
};
}
})