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bonus-parallel.js
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70 lines (66 loc) · 1.37 KB
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/**
* @param hash is an hash of names to functions
* @param callback is the final function
*/
function parallel(hash, callback) {
var i = 0;
var count = 0;
var retval = {};
var cb = function(err, key, data) {
if (err) {
callback(err);
// replace callback with noop so the final
// callback will only be executed once
callback = function() {};
} else {
i += 1;
retval[key] = data;
if (i === count) {
callback(null, retval);
}
}
};
// Count the number of functions
var key;
for (key in hash) {
if (hash.hasOwnProperty(key)) {
count += 1;
}
}
// Dispatch functions
for (key in hash) {
if (hash.hasOwnProperty(key)) {
hash[key](function(err, data) {
cb(err, key, data);
});
}
}
}
// example with non-erroring tasks
parallel({
first: function(callback) {
callback(null, {
piece: 'of data'
});
},
second: function(callback) {
callback(null, {
piece: 'of data'
});
}
}, function(err, data) {
console.log(err, data);
// > null { first: { piece: 'of data' }, second: { piece: 'of data' } }
});
parallel({
first: function(callback) {
callback(null, {
piece: 'of data'
});
},
second: function(callback) {
callback('well shit');
}
}, function(err, data) {
console.log(err, data); // > well shit undefined
});