Promise.all
var p1 = new Promise((resolve, reject) => {
setTimeout(resolve, 1000, "one");
});
var p2 = new Promise((resolve, reject) => {
setTimeout(resolve, 2000, "two");
});
var p3 = new Promise((resolve, reject) => {
setTimeout(resolve, 3000, "three");
});
var p4 = new Promise((resolve, reject) => {
setTimeout(resolve, 4000, "four");
});
var p5 = new Promise((resolve, reject) => {
reject("reject");
});
Promise.all([p1, p2, p3, p4, p5]).then(values => {
console.log(values);
}, reason => {
console.log(reason)
});
//From console:
//"reject"
// Evenly, it's possible to use .catch
Promise.all([p1, p2, p3, p4, p5]).then(values => {
console.log(values);
}).catch(reason => {
console.log(reason)
});
//From console:
//"reject"
const durations = [1000, 2000, 3000]
promises = durations.map((duration) => {
return timeOut(duration).catch(e => e) // Handling the error for each promise.
})
Promise.all(promises)
.then(response => console.log(response)) // ["Completed in 1000", "Rejected in 2000", "Completed in 3000"]
.catch(error => console.log(`Error in executing ${error}`))
view raw
// A simple promise that resolves after a given time
const timeOut = (t) => {
return new Promise((resolve, reject) => {
setTimeout(() => {
if (t === 2000) {
reject(`Rejected in ${t}`)
} else {
resolve(`Completed in ${t}`)
}
}, t)
})
}
const durations = [1000, 2000, 3000]
const promises = []
durations.map((duration) => {
promises.push(timeOut(duration))
})
// We are passing an array of pending promises to Promise.all
Promise.all(promises)
.then(response => console.log(response)) // Promise.all cannot be resolved, as one of the promises passed got rejected.
.catch(error => console.log(`Error in executing ${error}`)) // Promise.all throws an error.
// A simple promise that resolves after a given time
const timeOut = (t) => {
return new Promise((resolve, reject) => {
setTimeout(() => {
resolve(`Completed in ${t}`)
}, t)
})
}
// Resolving a normal promise.
timeOut(1000)
.then(result => console.log(result)) // Completed in 1000
// Promise.all
Promise.all([timeOut(1000), timeOut(2000)])
.then(result => console.log(result)) // ["Completed in 1000", "Completed in 2000"]
var arr = [
{subarr: [1,2,3]},
{subarr: [4,5,6]},
{subarr: [7,8,9]}
];
function processAsync(n) {
return new Promise(function(resolve) {
setTimeout(
function() { resolve(n * n); },
Math.random() * 1e3
);
});
}
Promise.all(arr.map(function(entity){
return Promise.all(entity.subarr.map(function(item){
return processAsync(item);
}));
})).then(function(data) {
console.log(data);
});