How can I write synchronous code in nodejs?

Question

I know it's a bad practice, but it would be helpful to know how to deal with certain cases.

In my case I'm trying to create some files, then read them. I'm wondering how can I wait for the creation to complete, before I try to read their containing directory, without using setTimeout and conditions?

Are you saying that you are creating files, and then look to see if they exist, and that there is a race condition, such that they may not yet exist? And is it because you are doing it in two synchronise threads/co-routines? Please add detail to question. — ctrl-alt-delor
– ctrl-alt-delor, Commented Nov 25, 2018 at 13:37
in my case I'm reading base64 data ,decoding it ,creating files with those data and trying to read those file after their creation , since the creation takes some time the fs.readdirsync is reading an empty folder, any trick would be very much helpful i've already tried the promises , co , async and many more — moxched
– moxched, Commented Nov 25, 2018 at 13:42

Milanzor · Accepted Answer · 2018-11-27 14:09:23Z

A lot of NodeJS function have synchronous counterparts, you should look for those.

Have a look at the documentation for File System at https://nodejs.org/api/fs.html. Do a page search for 'sync' and you can see that it offers many synchronous functions.

It's not just File System that offer this. The Child_process does the same, see https://nodejs.org/api/child_process.html#child_process_child_process_execsync_command_options for example.

If you can't find a native synchronous version of a function you need, the npm registry is a good place to look, a lot of times you can find a synchronous package there.

Good luck!

p.s. It's not always bad practice to write synchronous code in NodeJS, many CLI tools are synchronous for example.

bharat bhushan · Accepted Answer · 2018-11-25 13:41:37Z

0

You can use async await or promise to accomplish it

Example:-

async function f() {
  return 1;
}

You can pass your method inside it. it will wait till your response comes

answered Nov 25, 2018 at 13:41

bharat bhushan

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2 Comments

moxched Over a year ago

usualy in promisses you have to specify when to resolve and when to reject with a condition if my condition goes something like if (fs.readdirsync(directory) === DataFiles.length){resolve} it would never goes into it because the directory is still empty

ctrl-alt-delor Over a year ago

I think the OP will need a better example. They have tried promises. Can you show them how. (I don't use node.js, so won't get it right.)

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