for of array of promise

for-of-array-of-promise.js

let a=[10,20,30,40]

let getit=async(ax,ix,arr)=>{
    //console.log(ax,ix,arr)
    let time=Math.random()*3000;
    let ret=Math.random()>0.3;
    console.log(ix,arr[ix],time,ret);
    return new Promise((res,rej)=>{
        setTimeout(()=>{
            if (ret) {
                res({msg:"done ",val:arr[ix]});
                return
                     }
            else     {
                rej({msg:"error",val:arr[ix]});
                return
                     }
        },time)
    })}

// print promises after all settled, and in the order they are in the array
for (let prm of await Promise.allSettled(a.map( (ax,ix,arr)=>getit(ax,ix,arr) )) ){
    console.log(prm)
}

// use results after all promises settled, and in the order they are in the array
for (let prm of await Promise.allSettled(a.map( (ax,ix,arr)=>getit(ax,ix,arr) )) ){
    switch(prm.status){
        case "fulfilled":
            console.log(prm.value)
            break;
        case "rejected":
            console.error(prm.reason)
            break;
    }
}

// prints the promises
// causes "Uncaught (in promise)" error printed
for (let prm of await a.map( (ax,ix,arr)=>getit(ax,ix,arr) ) ){
    console.log(prm)
}

// processes the promises, but in the order they resolved/rejected
for (let prm of await a.map( (ax,ix,arr)=>getit(ax,ix,arr) ) ){
    prm.then(console.log).catch(console.error)
}

// process promises, but in the order they resolved/rejected
for (let prm of a.map( (ax,ix,arr)=>getit(ax,ix,arr) ) ){
    prm.then(console.log).catch(console.error)
}

// for await of, competely different behaviour, halts on first rejection
// uses results, and in the order they are in the array
// causes "Uncaught" in for before halting, and "Uncaught (in promise)" error in promises
for await (let prm of a.map( (ax,ix,arr)=>getit(ax,ix,arr) ) ){
    console.log(prm)
}

// exits loop in first rejection, else process results in the order they are in the array
for (let prm of await Promise.all(a.map( (ax,ix,arr)=>getit(ax,ix,arr) ) ) ){
    console.log(prm)
}