CODEWITHSUNDEEP
javascriptnode.jssplit
Kevin
Kevin

Reputation: 23

Why is the split method for Strings executed synchronously in NodeJS?

I'm new to NodeJS and am having a little trouble understanding what types of actions/tasks are executed asynchronously vs. synchronously. The specific example that I was working through was splitting a string.

I was trying to count the number of new lines in a block of text and then print that out. The below example worked. However, I'm not entirely clear why. My basic (and likely flawed) understanding is that anything that takes time is executed asynchronously (e.g. I/O), but I don't know what types of actions count as "taking time". Does the Split() method "take time"? It has to loop through the contents of a string, and if the string is abnormally long, this could take a while, why does this execute synchronously then or is it just that the split method blocks?

My question here is specific to the split method, but if anyone could also talk about or point me in the direction of some documentation that explains what gets executed synchronously vs asynchronously, it'd really appreciated!

var array = "test\nstring\nexample".split("\n");
console.log(array.length-1);

Upvotes: 2

Views: 1829

Answers (2)

Ian
Ian

Reputation: 34509

Essentially JavaScript is single threaded. The best advice is to assume it is single threaded unless something suggests otherwise.

Functions that aren't synchronous tend to accept a callback parameter to be executed. Examples of these would be a jQuery.ajax call or the setTimeout function.

Upvotes: 0

mscdex
mscdex

Reputation: 106736

Most operations in JavaScript itself are synchronous. The exceptions include the obvious ones such as setTimeout(), setInterval(), requestAnimationFrame(), etc. Also just because you pass in a callback does not mean the function is asynchronous (for example see some of the array methods, like array.forEach(), array.map(), array.filter(), array.some(), etc.).

Node.js (core), which builds on top of JavaScript (via the v8 engine), adds its own synchronous and asynchronous methods. However fairly early on it was decided to distinguish between the two by way of an easily visible Sync suffix to functions that perform synchronously. However, similar to JavaScript, there are some exceptions (e.g. require()). It should also be noted that userland modules (on npm for example) may have their own convention (or none at all), so for those third party modules you will need to read the documentation to be sure of the behavior of their exported functions.

Upvotes: 1

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