If you notice it calls my sleep function, and basically retries the HTTP call in 5 second intervals. So to start off with I originally had an API call that looked like this:Įnter fullscreen mode Exit fullscreen mode In this post I'm just going to show what I did, and how you can use this in your programs. I liked my function because it was very simple and I understood what it was doing end to end. There are several ways to do this (and npm packages as well). So to do this I built a custom "sleep" function. Otherwise, it would force my API to fail as a result. Regardless, I needed to build in some mechanism to handle this behavior. My assumption was this was based on load etc. This was pretty frustrating because it would happen at different points in the day. What I noticed in testing was that if it failed, but I waited a few seconds and tried again, it worked. The issue I had was that one of the API calls would intermittently fail. I'm using some of the NOAA Endpoints that you can see here. Recently, I was working on an NodeJS API that calls a set of endpoints to provide a weather forecast. I actually cover a basic walkthrough of this in my post Optimizing Angular with Async Await. Which forces things that are async (like promises) to complete before getting a payload and making calls. One common approach to handling things like this is using async await. It makes it harder when you want to streamline processing to force control on things like threads or API calls. This means that things like scope and order can make or break JavaScript programs.
#Nodejs sleep code#
Unlike many other languages, JavaScript operates inside a hosted environment which determines how the code is actually ran. When learning JavaScript for the first time, one of the biggest challenges is understanding the event loop. They're showing what a well rested NodeJS function looks like. log ( "Hello" ) setTimeout ( ( ) => delayedGreeting ( ) console. The standard way of creating a delay in JavaScript is to use its setTimeout method. Now that we have a better understanding of JavaScript’s execution model, let’s have a look at how JavaScript handles delays and asynchronous operations. You Might Not Actually Need a JS Sleep Function If any of this is news to you, you should watch this excellent conference talk: What the heck is the event loop anyway?. Rather, it will continue on its way, output “Hello!” to the console, then when the request returns a couple of hundred milliseconds later, it will output the number of repos. It will not, however, wait for the request to complete. The JavaScript interpreter will encounter the fetch command and dispatch the request. This is because fetching data from an API is an asynchronous operation in JavaScript. If you run this code, it will output “Hello!” to the screen, then the number of public repos attributed to my GitHub account. Execution goes from top to bottom.Ĭontrast that with the equivalent JavaScript version: fetch ( '' ). It then parses the response, outputs the number of public repos attributed to my GitHub account and finally prints “Hello!” to the screen. get (uri ) )Īs one might expect, this code makes a request to the GitHub API to fetch my user data. Understanding JavaScript’s Execution Modelīefore we get going, it’s important to make sure we understand JavaScript’s execution model correctly.Ĭonsider the following Ruby code: require 'net/http' require 'json'
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