Pfthb

for example am trying to recursively get the file size of all items under a folder in cordova so i have something like

getDirSize(path) 
 return this.listDir(path).then((data) => 
 let size = 0

 data.dirs.map((dir) => 
 size += this.getRecursiveSize(dir.files)
 )

 if (data.files.length) 
 size += this.getRecursiveSize(data.files)
 

 return size
 )


getRecursiveSize(files) 
 let size = 0

 files.map((item) => 
 this.getFileMeta(item.url).then((file) => 
 size += file.size
 )

 if (item.files) 
 size += this.getRecursiveSize(item.files)
 
 )

 return size

which is called through

getDirSize(path).then((size) => 
 console.log(size)
)

however this doesn't work because the getFileMeta() is a promise, i know about promise.all() but am not sure how to use it properly to get the final size of all items.

So you can put all of the calls to getFileMeta() into an array using map and Promise.all. Promise.all will take a an array of promises and set whatever is resolved within each into an array.

So you get back an array of fileMetaData in this case, which you can use as any other array (after the Promise.all is finished -- using .then or await)..

If it (aka getFileMeta) already returns a promise:

const filesMetaData = Promise.all(files.map(file => this.getFileMeta(file.url)))
filesMetaData.then(
fileMetaData // became an array here because of Promise.all
=> fileMetaData.reduce((accumulatedSize, file) => 
 accumulatedSize += file.size
 return accumulatedSize
)

Or if you are using a later version of node then you can use asynchronous javascript with async/await which is pretty cool!

In pseudo-code the strategy is:

1. Await getting the fileMetaData about EACH one of the files.


2. Get each one of the original files' sizes and add those to 0.


3. Check for if any files have nested files within.


4. If so add those files to a list of files to recursively run this function.


5. If none of the files have nested files return the count for the parent files.

const recursivelyGetSize = async (files) => 
 if (!files.length) // recursive condition 
 return 0
 
 const filesMetaData = await Promise.all(
 files.map(file => this.getFileMeta(file.url))
 ) // became an array of files here because of Promise.all
 const count = fileMetaData.reduce(
 (accumulatedSize, file) => accumulatedSize + file.size,
 0
 )
 const filesWithFiles = filesMetaData.filter(file => file.files.length)
 if (!filesWithFiles.length) 
 return count
 
 // not sure if you need await here because
 // return by default has a built in await
 return count + await recursivelyGetSize([
 ...filesWithFiles.map(file => file.files)
 ])