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batchasync.js
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AJ ONeal 2019-11-25 15:38:55 -07:00
parent 038b6cac33
commit dd206891d5
1 changed files with 63 additions and 64 deletions
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batchasync.js
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@ -1,71 +1,70 @@
(function (exports) { (function(exports) {
'use strict'; "use strict";
exports.batchAsync = function (limit, arr, doStuff) { exports.batchAsync = function(limit, arr, doStuff) {
arr = arr.slice(0); arr = arr.slice(0);
return new Promise(function(resolve, reject) { return new Promise(function(resolve, reject) {
var total = arr.length; var total = arr.length;
var active = 0; var active = 0;
var results = []; var results = [];
var error; var error;
function doMoreStuff() { function doMoreStuff() {
// Don't take on any more tasks if we've errored, // Don't take on any more tasks if we've errored,
// or if too many are already in progress // or if too many are already in progress
if (error || active > limit) { if (error || active > limit) {
return; return;
} }
// If there are no more tasks to start, return // If there are no more tasks to start, return
if (!arr.length) { if (!arr.length) {
// If everything is also *finished*, resolve // If everything is also *finished*, resolve
if (active < 1) { if (active < 1) {
resolve(results); resolve(results);
} }
return; return;
} }
// We need to dequeue the task here so the index is correct // We need to dequeue the task here so the index is correct
// (keep in mind we want to support sync and async) // (keep in mind we want to support sync and async)
var index = total - arr.length; var index = total - arr.length;
var task = arr.shift(); var task = arr.shift();
active += 1; active += 1;
// Spawn another task immediately, // Spawn another task immediately,
// which will be stopped if we're at the limit // which will be stopped if we're at the limit
doMoreStuff(); doMoreStuff();
var p; var p;
try { try {
p = doStuff(task); p = doStuff(task);
} catch (e) { } catch (e) {
// we need to handle, and bubble, synchronous errors // we need to handle, and bubble, synchronous errors
error = e; error = e;
reject(e); reject(e);
throw e; throw e;
} }
// Do stuff and then decrease the active counter when done // Do stuff and then decrease the active counter when done
// add support for sync by rapping in a promise // add support for sync by rapping in a promise
Promise.resolve(p) Promise.resolve(p)
.then(function(result) { .then(function(result) {
if ('undefined' === typeof result) { if ("undefined" === typeof result) {
throw new Error( throw new Error(
"result was 'undefined'. Please return 'null' to signal that you didn't just forget to return another promise." "result was 'undefined'. Please return 'null' to signal that you didn't just forget to return another promise."
); );
} }
active -= 1; active -= 1;
results[index] = result; results[index] = result;
}) })
.then(doMoreStuff) .then(doMoreStuff)
.catch(function(e) { .catch(function(e) {
// handle async errors // handle async errors
error = e; error = e;
reject(e); reject(e);
}); });
} }
doMoreStuff(); doMoreStuff();
}); });
}; };
})("undefined" !== typeof window ? window : module.exports);
}('undefined' !== typeof window ? window : module.exports));