1/*
2	A Promise is a proxy for a value not necessarily known when the promise is created. 
3    It allows you to associate handlers with an asynchronous action's eventual success 
4    value or failure reason.
5*/            
6let promise = new Promise((resolve , reject) => {
7  fetch("https://myAPI")
8    .then((res) => {
9      // successfully got data
10      resolve(res);
11    })
12    .catch((err) => {
13      // an error occured
14      reject(err);
15    });          
16});

1function doSomething() {
2  return new Promise((resolve, reject) => {
3    console.log("It is done.");
4    // Succeed half of the time.
5    if (Math.random() > .5) {
6      resolve("SUCCESS")
7    } else {
8      reject("FAILURE")
9    }
10  })
11}
12
13const promise = doSomething(); 
14promise.then(successCallback, failureCallback);

1//create a Promise
2var p1 = new Promise(function(resolve, reject) {
3  resolve("Success");
4});
5
6//Execute the body of the promise which call resolve
7//So it execute then, inside then there's a throw
8//that get capture by catch
9p1.then(function(value) {
10  console.log(value); // "Success!"
11  throw "oh, no!";
12}).catch(function(e) {
13  console.log(e); // "oh, no!"
14});
15

1new Promise( (res, rej) => {
2  setTimeout(() => res(1), 1000);
3}).then( (res) => {
4  console.log(res); // 1
5  return res*2
6}).then( (res) => {
7  console.log(res); // 2
8});
9

1var promise = new Promise(function(resolve, reject) {
2  // do some long running async thing…
3  
4  if (/* everything turned out fine */) {
5    resolve("Stuff worked!");
6  }
7  else {
8    reject(Error("It broke"));
9  }
10});
11
12//usage
13promise.then(
14  function(result) { /* handle a successful result */ },
15  function(error) { /* handle an error */ }
16);

1const someThing = new Promise((resolve, reject) => {
2  //Example Axios is used
3            axios
4               .get("/get-some-data-some-some-where")
5               .then(function({ data }) {
6                   resolve(data);
7                })
8               .catch(error => {
9                   reject(error);
10                });
11            });
12
13const someThingTwo = new Promise((resolve, reject) => {
14  //Example Axios is used
15            axios
16               .get("/get-some-data-from-somewhere-else")
17               .then(function({ data }) {
18                   resolve(data);
19                })
20               .catch(error => {
21                   reject(error);
22                });
23            });
24
25
26Promise.all([someThing, someThingTwo]).then(
27                res => {
28                    const SomeVariable = res[0]; //Data from someThing
29                    const SomeVariable2 = res[1]; //Data from someThingTwo
30
31                },
32                error => {
33                   console.log(error)
34                }
35            );