promise all in promise all
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); });
promise.all
// 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.
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