Is variable assignment synchronous in nodejs?

Question

Say we have

var x =3; 
var y = 4;
var z = x*y;
console.log(z);

How do we know it won't print an undefined variable z?

If it is asynchronous, is there a function used to assign values to variables with a callback so we can be certain of their values when using them.
If it is synchronous, then when loading modules like

var express = require('express');

Wouldn't that be pretty slow when you load a few of them in one script?

Possible duplicate of Are JavaScript functions asynchronous?. This thread should clear up any questions you have. — Robert Moskal
– Robert Moskal, Commented May 11, 2016 at 1:30
So nodejs is just normal javascript? I thought the entire point was that it is executed asynchronously. That still doesn't answer my question of whether it is slow to load multiple requires in one script. — SirKaliKook
– SirKaliKook, Commented May 11, 2016 at 1:49
when you load modules with require most of the time it is not over the network (The files are on the server) so it wont be a long time. You might be thinking about requesting over the network which has latency. — jack blank
– jack blank, Commented May 11, 2016 at 2:06

user663031 · Accepted Answer · 2016-05-11 03:35:55Z

9

Is variable assignment synchronous in nodejs?

Yes, it is.

Actually, any sequence of statements is executed synchronously.

You may be getting confused with the following type of situation:

var x = LongRunningAsyncTask();
console.log(x);

Here, LongRunningAsyncTask cannot return its result, since it is not yet known. Therefore, x probably won't be what you want, which is why, assuming LongRunningAsyncTask is implemented in callback style, you need to write

LongRunningAsyncTask(function callback(x) {
  console.log(x);
});

or if LongRunningAsyncTask returns a promise, then

LongRunningAsyncTask() . then(x => console.log(x));

or using async functions:

async function foo() {
  var x = await LongRunningAsyncTask();
  console.log(x);
}

answered May 11, 2016 at 3:35

user663031

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