How to handle sync browser emulations in node.js - node.js

Question

I'm writing a script that is intended to load some stuff from .txt files and then perform multiple ( in a loop) requests to a website with node.js` browser emulator nightmare.
I have no problem with reading from the txt files and so no, but managing to make it run sync and without exceptions.
function visitPage(url, code) {
new Promise((resolve, reject) => {
Nightmare
.goto(url)
.click('.vote')
.insert('input[name=username]', 'testadmin')
.insert('.test-code-verify', code)
.click('.button.vote.submit')
.wait('.tag.vote.disabled,.validation-error')
.evaluate(() => document.querySelector('.validation -error').innerHTML)
.end()
.then(text => {
return text;
})
});
}
async function myBackEndLogic() {
try {
var br = 0, user, proxy, current, agent;
while(br < loops){
current = Math.floor(Math.random() * (maxLoops-br-1));
/*...getting user and so on..*/
const response = await visitPage('https://example.com/admin/login',"code")
br++;
}
} catch (error) {
console.error('ERROR:');
console.error(error);
}
}
myBackEndLogic();
The error that occurs is:
UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'webContents' of undefined
So the questions are a few:
1) How to fix the exception
2) How to make it actually work sync and emulate everytime the address ( as in a previous attempt, which I didn't save, I fixed the exception, but the browser wasn't actually openning and it was basically skipped
3) (Not so important) Is it possible to select a few objects with
.wait('.class1,.class2,.validation-error')
and save each value in different variables or just get the text from the first that occured? ( if no any of these has occurred, then return 0 for example )

Answer 1

I see a few issues with the code above.
In the visitPage function, you are returning a Promise. That's fine, except you don't have to create the wrapping promise! It looks like nightmare returns a promise for you. Today, you're dropping an errors that promise returns by wrapping it. Instead - just use an async function!
async function visitPage(url, code) {
return Nightmare
.goto(url)
.click('.vote')
.insert('input[name=username]', 'testadmin')
.insert('.test-code-verify', code)
.click('.button.vote.submit')
.wait('.tag.vote.disabled,.validation-error')
.evaluate(() => document.querySelector('.validation -error').innerHTML)
.end();
}
You probably don't want to wrap the content of this method in a 'try/catch'. Just let the promises flow :)
async function myBackEndLogic() {
var br = 0, user, proxy, current, agent;
while(br < loops){
current = Math.floor(Math.random() * (maxLoops-br-1));
const response = await visitPage('https://example.com/admin/login',"code")
br++;
}
}
When you run your method - make sure to include a catch! Or a then! Otherwise, your app may exit early.
myBackEndLogic()
.then(() => console.log('donesies!'))
.catch(console.error);
I'm not sure if any of this will help with your specific issue, but hopefully it gets you on the right path :)