forloop

Node.js non-blocking for ( ; ; ) loop for long running tasks.

Introduction

Node.js is an asynchronous event driven framework for the V8 JavaScript engine. CPU-intensive task in your code will block the current thread of execution, including the event loop. Blocking the event loop can have catastrophic effects on the Node application.

What is wrong with vanilla for loop?

Nothing.

This library tackles the use case where CPU-intensive code block is executed repetitively inside a loop.

Installation

$ npm install forloop

Usage

forloop(initialization, limit, increment, iterationCallback, finalCallback)

Arguments

• initialization - Initial value for the counter variable.
• limit - The final value of the counter to break the loop.
• increment - The value to increment the counter variable.
• iterationCallback(i) - A function to call on each itertation of the loop. The current value of the counter variable is passed as the argument.
• finalCallback() - A function, which is called when the loop exits.

Example

Calculating Golden Ratio

Bad

var count = 10000000;
var φ = 0;
 
for (var i = 0; i < count; i++) {
    φ = Math.sqrt(φ + Math.sqrt(1));
}
 
console.log("φ ≈ %d", φ);

Good

var forloop = require('forloop');
var count = 10000000;
var φ = 0;
 
forloop(0, count, 1,
        function(i) {
            φ = Math.sqrt(φ + Math.sqrt(1));
        },
        function() {
            console.log("φ ≈ %d", φ);
        }
);

Test

$ npm test

License

MIT