I'm building a server in Node that will search a folder to see if an XML file exists (glob), and if it does, read the file in (fs) as a JSON object (xml2js) and eventually store it in a database somewhere. I'm want to get the results OUT of the parser and into another variable so I can do other things with the data. From what I can tell, something is running synchronously, but I can't figure out how to stop it and for me to wait until it's finished to continue moving on.
I'm separating my function out into a controller elsewhere from app.js:
app.controller.js
const fs = require('fs-extra');
const glob = require('glob');
const xml2js = require('xml2js');
exports.requests = {};
exports.checkFileDrop = async () => {
console.log('Checking for xml in filedrop...');
// this is the only place await works...
await glob('./filedrop/ALLREQUESTS-*.xml', (err, files) => {
var parser = new xml2js.Parser();
// this is looking for a specific file now, which I'll address later once I can figure out this issue
fs.readFile('./filedrop/ALLREQUESTS-20170707.xml', 'utf16le', function (err, data) {
if (err) {
console.log('ERROR: ', err);
} else {
parser.parseString(data, (err, result) => {
if (err) {
console.log('ERROR: ', err);
} else {
console.log('data found');
exports.requests = JSON.stringify(result.Records.Record);
// data is outputted here correctly
console.log(exports.requests);
// this doesn't even seem to want to save to exports.requests anyways...
}
});
}
});
});
}
app.js
const appController = require('./controllers/app.controller');
// check if there is file in filedrop
appController.checkFileDrop();
// prints out an empty object
console.log(appController.requests);
// can't do anything if it doesn't exist yet
appController.saveToDB(appController.requests);
I'm building a server in Node that will search a folder to see if an XML file exists (glob), and if it does, read the file in (fs) as a JSON object (xml2js) and eventually store it in a database somewhere. I'm want to get the results OUT of the parser and into another variable so I can do other things with the data. From what I can tell, something is running synchronously, but I can't figure out how to stop it and for me to wait until it's finished to continue moving on.
I'm separating my function out into a controller elsewhere from app.js:
app.controller.js
const fs = require('fs-extra');
const glob = require('glob');
const xml2js = require('xml2js');
exports.requests = {};
exports.checkFileDrop = async () => {
console.log('Checking for xml in filedrop...');
// this is the only place await works...
await glob('./filedrop/ALLREQUESTS-*.xml', (err, files) => {
var parser = new xml2js.Parser();
// this is looking for a specific file now, which I'll address later once I can figure out this issue
fs.readFile('./filedrop/ALLREQUESTS-20170707.xml', 'utf16le', function (err, data) {
if (err) {
console.log('ERROR: ', err);
} else {
parser.parseString(data, (err, result) => {
if (err) {
console.log('ERROR: ', err);
} else {
console.log('data found');
exports.requests = JSON.stringify(result.Records.Record);
// data is outputted here correctly
console.log(exports.requests);
// this doesn't even seem to want to save to exports.requests anyways...
}
});
}
});
});
}
app.js
const appController = require('./controllers/app.controller');
// check if there is file in filedrop
appController.checkFileDrop();
// prints out an empty object
console.log(appController.requests);
// can't do anything if it doesn't exist yet
appController.saveToDB(appController.requests);
2 Answers
Reset to default 17await will wait for a Promise value to resolve, otherwise it'll just wrap the value it is given in a promise and resolve the promise right away. In your example,
await glob('./filedrop/ALLREQUESTS-*.xml', (err, files) => {
the call to glob does not return a Promise, so the await is essentially useless. So you need to create the promise yourself.
exports.checkFileDrop = async () => {
console.log('Checking for xml in filedrop...');
const files = await new Promise((resolve, reject) => glob('./filedrop/ALLREQUESTS-*.xml', (err, files) => {
if (err) reject(err);
else resolve(files);
});
const parser = new xml2js.Parser();
const data = await new Promise((resolve, reject) => fs.readFile('./filedrop/ALLREQUESTS-20170707.xml', 'utf16le', function (err, data) {
if (err) reject(err);
else resolve(data);
});
const result = await new Promise((resolve, reject) => parser.parseString(data, (err, result) => {
if (err) reject(err);
else resolve(result);
});
console.log('data found');
const requests = JSON.stringify(result.Records.Record);
console.log(requests);
}
Note that now this function will reject the promise it returns instead of force-logging the error.
You can also condense this down with a helper. Node 8 for instance includes util.promisify to make code like this easier to write, e.g.
const util = require('util');
exports.checkFileDrop = async () => {
console.log('Checking for xml in filedrop...');
const files = await util.promisify(glob)('./filedrop/ALLREQUESTS-*.xml');
const parser = new xml2js.Parser();
const data = await util.promisify(fs.readFile)('./filedrop/ALLREQUESTS-20170707.xml', 'utf16le');
const result = await util.promisify(parser.parseString.bind(parser))(data);
console.log('data found');
const requests = JSON.stringify(result.Records.Record);
console.log(requests);
}
You can use async/await
import fs from 'fs';
import { promisify } from 'util';
const xmlToJson = async filePath => {
const parser = new xml2js.Parser
try {
const data = await fs.promises.readFile(filePath, 'utf8')
const result = await promisify(parser.parseString)(data);
const requests = JSON.stringify(result.merchandiser.product);
return requests
}
catch(err) {
console.log(err)
}
}