function, that returns Promise - node.js

Question

I have a task with a promise and I don't understand how to do it.please help
1.Imports function "func1" from file "script1.js";
const func1 = a => {
switch (a) {
case 'a':
return new Promise((resolve) => {
setTimeout(() => {
resolve('result1');
}, 100);
});
case 'b':
return new Promise((resolve) => {
setTimeout(() => {
resolve('result2');
}, 100);
});
default:
return new Promise((resolve) => {
setTimeout(() => {
resolve('result3');
}, 100);
});
};
};
module.exports = func1;
Reads a string from the "input.txt";
input a
Calls "func1" with an argument equal to the string;
Waits until the received Promise has state: "fulfilled" and then outputs the result to the file "output.txt".
this is how i try to solve but nothing works:
const fs = require('fs')
const func1 =require ("./script1 (1)")
fs.readFile('./input.txt', 'utf8' , (err, data) => {
if (err) {
console.error(err)
return
}
console.log(data)
async function one (data) {
try {
const result = await Promise(func1);
console.log(result);
} catch (err) {
console.log(err)
}}
fs.writeFile("output.txt",one().toString(), function(err)
{
if (err)
{
return console.error(err);
}
})
})
the result must be "result1"

Answer 1

To call a Promise you can use async await and try catch blocks. Once you have the asynchronous result value, you can call fs.writeFile(). Try this:
func1.js:
const func1 = a => {
switch (a) {
case 'a': return new Promise((resolve) => {
setTimeout(() => { resolve('result1'); }, 100);
});
case 'b': return new Promise((resolve) => {
setTimeout(() => { resolve('result2'); }, 100);
});
default: return new Promise((resolve) => {
setTimeout(() => { resolve('result3'); }, 100);
});
};
};
module.exports = func1;
index.js:
const fs = require('fs');
const func1 = require("./demo2.js")
fs.readFile('./input.txt', 'utf8' , async (err, data) => {
if (err) {
console.error(err);
return;
}
//console.log(data)
try {
const result = await func1(data);
console.log(result);
fs.writeFile("output.txt", result, function(err) {
if (err){
return console.error(err);
}
});
} catch (err) {
console.log(err)
}
});

Answer 2

the async/await way is to change const result = await Promise(func1); to const result = await func1(data); you can also use then like this const result = func1(data).then(res => res);
and a better func1 would be
const func1 = a => {
return new Promise((resolve) => {
setTimeout(() => {
switch(a) { // handle cases };
});
});
};
module.exports = func1;

Answer 3

const func1 = a => {
return new Promise((resolve) => {
switch (a) {
case 'a':
setTimeout(() => {
resolve('result1');
}, 100);
case 'b':
setTimeout(() => {
resolve('result2');
}, 100);
default:
setTimeout(() => {
resolve('result3');
}, 100);
};
})
};
module.exports = func1;
const fs = require('fs')
const func1 =require ("./script1 (1)")
fs.readFile("./input.txt", "utf8", (err, data) => {
if (err) {
console.error(err);
return;
}
console.log(data);
async function one(data) {
try {
func1(data).then(result => {
console.log(result)
})
} catch (err) {
console.log(err);
}
}
fs.writeFile("output.txt", one().toString(), function (err) {
if (err) {
return console.error(err);
}
});
});