Promise.map memory issue

When use the Promise.map() to iterate a list, the memory will not be freed up until the all the task finished. That means the GC only works after the callback of the Promise.map(). When the list is huge, there will be a big problem on memory usage.

To avoid this issue, can use _.churk() to spilt the huge list to small one. And use the Promise.map() to iterate the small list. There will no memory issue any more.”

Ref to the following sample code:

function map(list, fn, option) {
var concurrency = list.length;
if (option && option.concurrency){
concurrency = option.concurrency;
}
var chunk = _.chunk(list, concurrency);
return mapChunk(chunk, 0, fn);
}
 
function mapChunk(chunk, i, fn) {
return Promise.map(chunk[i], fn)
.then(() => Promise.delay(1).then(() => {
i++; if (i < chunk.length) {
return mapChunk(chunk, i, fn);
} else {
return Promise.resolve();
}});}