promise_in_for.js

// https://stackoverflow.com/questions/48014050/wait-promise-inside-for-loop
// let each promise in for to finish
function test(n) {
   let promiseChain = Promise.resolve();
    for (let i = 0; i < n; i++) { 
        const makePromise =  (j) => () => new Promise((resolve,reject)=> {
               setTimeout(resolve, j*1000);
        }).then(()=>{
          console.log(j); 
          if (j < 5 ) {
            return Promise.resolve(j);
          } else {
            return Promise.reject(j);
          }
        });           
        try {
          promiseChain = promiseChain.then(makePromise(i));
        } catch (err) {
          return Promise.reject(err);
        }
    }
    return promiseChain; 
}

test(8).then((x)=>{console.log(x+'x')}).catch((x)=>{console.log(x+' y')})