Category: Uncategorized

A Super quick guide to arrow functions

I added a video version of this blog. If you prefer video, check it out: https://youtu.be/HC2W75WMw6c

This is NOT a definitive guide to arrow functions. I’m writing a few other tutorials and blogs and want to have something to point people to so they can have a quick explanation and example of arrow functions since they are in so many of the modern frameworks. Just enough to be dangerous! To be clear, there are reasons where you should not use arrow functions, but they are not going to be discussed in this blog post. I just want you to be able to know how they work when you see them “in the wild”.

Let’s get started. I’m going to take you step by step converting a regular function into an arrow function.

Here’s a regular function using the function keyword

Let’s change that to an anonymous function expression

Should be nothing new here so far. No Arrows or ES6 yet, but here it comes…

First remove the function keyword and add the arrow

The only thing going on there is removing the function keyword and adding the arrow. And that’s it! You’ve gone and made an arrow function! Hurray! But wait, there’s more!

If there is only one argument, you can get rid of the parentheses around it.

Getting pretty lean but we can take it even further. If the body of the code is only one line, we can get rid of the curly braces.

Frequently, you’ll see these used as a callback in another function so there is no const and no function name. This is the case that we see quite a bit and the real reason I wrote this all up in the first place

This doesn’t do anything on its own, but as a callback it’s useful. Here we’re using as a callback for looping over an array with the forEach array method.

As a comparison, here’s a regular old for loop. Sure, we understand this as programmers, but the arrow function just reads like a sentence in normal language. So much easier to understand!

I think that covers the basics. Again this is not meant to be the definitive guide, just an intro to figure out what they mean because we see them ‘in the wild’ in all the modern frameworks.

How to fix Netlify “page not found, broken link or entered a URL that doesn’t exist” error

I made a simple React app with React router that worked while clicking the links in the nav, but not if you enter those URLs in the location bar.

Netlify – Page Not Found
Looks like you’ve followed a broken link or entered a URL that doesn’t exist on this site.

TLDR – make a file in the public directory called “_redirects” with this line in it

/* /index.html 200

What’s going on here?

Single page apps have one HTML file and everything is launched via Javascript from there. Routing is handled through the client, not the server so there is no file located at mySPA.com/about (for example). In a traditional HTML site /about would work if there was an index.html file in the /about directory. In an SPA however, something in the router code tells the browser what component/page to display when that route is asked for. So this file basically says “hey, anything you don’t find ( the * character) come back and look at the main index.html file, I’ve got router info there. Much success! (200)”

I found this page which says netlify only tries to serve the main index.html file https://community.netlify.com/t/common-issue-i-ve-deployed-my-site-but-i-still-see-page-not-found/125

This didn’t really solve my problem but it got me looking around through the forums and I found something that said you need to use “redirects” to handle those pages (the ones that look folders with no index page)

First I found something about putting config information in a netlify.toml file in the root directory of the project. For me, putting the reccommened line in that file failed on build. I came across something that said to put the “_redirects” in my root directory which also didn’t do anything. I ended up doing a lot of clicking around before I got my solution.

Eventually I found a page on the netlify blog that said the “_redirects” file needs to be in the build folder. https://www.netlify.com/blog/2019/01/16/redirect-rules-for-all-how-to-configure-redirects-for-your-static-site/

My problem here was how my build folder is also in my .gitignore file so it never gets uploaded to github and my site is being built from my git repo! Finally, I realized I could just put the “_redirects” file into the public directory (same place as the index.html file for the site)

I wrote this blog because it took me 20 minutes or more of searching to figure out how to implement 20 characters of code. I’m not complaining about netlify mind you, they are an amazing product. There are a million different combinations of frameworks and languages that they are trying to support so there may not be a simple answer to my particular case. I just had a hard time finding the short answer so I hope to save someone the time solving the same issue.

Thanks for reading!

How to prevent ejs from splitting a string in attribute-value pair in a form field

TL:DR – put quotes around your EJS value when it is being used as an HTML attribute

I was making a simple Express app with EJS templating and MongoDB for my REST API. I passed the response, which was a few strings and a date, to the view in the typical fashion, and I could verify that the data was being passed by outputting the object to the view like this: 

<%=responseObject%>
//which displayed this:
{ 
  _id: 5d347b004b0c201108909a55, 
  name: 'hot dogs', 
  description: 'costco dogs', 
  dateOnBag: '3/4/19', __v: 0 
}

This displayed the entire object on the screen. Additionally, I could display one of the object’s values using dot notation with no problem.

<h1>Edit <%=responseObject.name%></h1>
// which displayed this

Edit hot dogs

However, when I tried to use the same syntax to prefill a form field like this:

<li>
  <input type="text" name="name" value=<%-responeseObject.name%>><br />
  <label for="name">Item Name </label>
<li>

It pre-filled only the first word, “hot” instead of both words “hot dog”


I finally figured out that I needed to put quotes around it. When Express renders the page it simply replaces the EJS syntax with a string of text so the resulting HTML looked more like this:

  <input type="text" name="name" value=hot dog><br />

I later learned that HTML attribute values do not always need quotes. (basically, when there are no spaces) https://mathiasbynens.be/notes/unquoted-attribute-values So in the example above,

value=hot dog
//is equivalent to 
value="hot" dog

which leaves dog just hanging out there, an attribute without any value which HTML just ignores in this case. Actually, if I’m interpreting the spec correctly, it is setting the value of dog to true which is any case is not used so again it is ignored. https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes

Web Scraping with Cheerio.js

When learning web development, they all tell you to find a problem in your life and create a solution using code to create a great project. Well, I drive for Uber and I wanted to know when the most flights would be coming into my local airport. The airport website has listings, but it’s a cluttered mess. I wanted something where I could just see at a glance when the most flights were coming in. I could not find a public/free API for flight information so I needed to figure out a little bit of web scraping. Code and working example is here: https://codesandbox.io/s/7zx3v5kqmq and I did a video walk-through explaining how the code works here:

Algorithms!

I’ve been making more videos and this time I’ve been working on the freeCodeCamp selection of algorithm challenges. I’ve been doing one every day and adding them to the playlist below. I’m twelve days in and the plan is to do one every day until I’ve got them all!

Check out my youtube channel

I’ve been adding videos about JavaScript to my youtube channel and you can take a look at it here: https://www.youtube.com/channel/UCqdNQHOLz3PmB4cDvQkdQ1w/videos

They are not professionally produced.  I just turn on youtube and start typing generally.  You may have heard of “rubber duck decoding” and this is basically how I make these videos.  They are either me talking through some code I’ve just worked on or some are videos I’ve made where I’m trying to help a friend out with some coding issue.