Correct way of catching error in Promise objects - angular-promise

Question

Ok so I am newbie in Angularjs,one of my current task is to code a CRUD functionality and I used the Promise to handle it.
dao.updateEntityCharSpecUseRelSql = function (paramField) {
return new Promise(function (resolve, reject) {
.......
}).catch(err => { reject(err)});// **my PM says, catching error is wrong**
}
module.exports = dao;
First, I thought, catch block is just alright because I am getting it from the Promise object which returns the error if something goes wrong.
But my Pm says, in order to use this, promises should have .then() first.
Is it really a bad practice to use the catch() without then(). What he propose is that instead, I should create a try & catch block inside the Promise() something like
new Promise (function(resolve, reject){
try {
resolve(something)
}catch(err){
reject(err)
}
})
Please enlighten me for this.TIA

Answer 1

Let's do a step back.
When you create a new Promise() you are responsible to handle each success and failure case.
Who is calling your function (and getting your promise) is responsible to handle the response inside a then() callback, if the promise was successfully resolved, or a catch() callback, if the promise was rejected.
So, you don't need to catch your own promise.
Example:
function init() {
getAsyncValues()
.then(function (result) {
// it will do something based on his business logic
})
.catch(function (error) {
// it will do something based on his business logic
});
}
function getAsyncValues() {
return new Promise(function(resolve, reject) {
...
resolve(SOME_VALUES);
...
reject(SOME_ERRORS);
})
}
And if your "promise handler" need to call async task before resolving something, you can wait his resolution like:
const examplePromise = new Promise(fuction (resolve, reject) {
asyncTask() // executing an async task
.then(function(result) {
resolve(result);
})
.catch(function(error) {
reject(error)
});
})