SOURCE

var a = ["a","b","c","d"]
  var b = [];
  var c = [1000,200,1300,400];
for(let i=0;i<a.length;i++){
    let t = a[i];
    b.push(
      new Promise((resolve,reject)=>{
        setTimeout(()=>{
          console.log(t,i)
          resolve();
        },c[i])
      })
    )
  }