Js From Dom To Node

Congratulations! You are now able to understand how Javascript interacts with websites through the DOM. That's a big deal. Take a few seconds, breathe in, breathe out and realize that you now know something you didn't before. Only a few lessons ago, you didn't even know what the DOM was. Now you understand how to manipulate it.


If you ever want to show your friends something cool, open up the console on any web page and then find the selector for an element, then modify it using Javascript in the console. Prepare to enjoy the shock and awe of your friends!

From DOM Manipulation to Programming Logic

For the rest of this material, we will be moving from the basics of DOM manipulation to the meat and potatoes of programming. This means we are going to cover the ideas of conditionals, looping, encapsulation and syntax. I know those may not be familiar to you, but over the next few lessons they will become second nature! Remember when DOM was a scary word? Encapsulation will soon go the way of the DOM. You're going to be encapsulating everything.

Really the goal of the rest of this course is to introduce you to programmatic thinking. We will be doing that through explaining Javascript, but the goal is for every student to begin using programmatic thinking as a general way to solve problems. These problems may be creating the next Facebook, or it may be just solving the best order to complete your errands. You'll notice programmatic, logical thinking starting to permeate throughout your decision process. It's incredibly powerful and something that has aided millions of programmers to solve some of the hardest problems in the world.

That is the goal with this class. While we may touch on making pictures of cats spin, we want you to internalize the thought process required to solve that silly problem. Hopefully, you'll go off after this class and solve some slightly more important problems :)

Javascript Outside of the Browser

You've spent some time in the browser with Javascript. That's great. Now let's get to where Javascript has been rapidly increasing its programming market share: outside of the browser. You may have heard of it, but a new tool called NodeJS was created a few years back to allow developers to write Javascript code outside of the browser. That is what we are going to use now to be able to go deep on programmatic thinking, without having to explain complicated browser interactions. We want to simplify programming down to its most core elements.

Hello World

Let's write your first code using NodeJS and non-browser Javascript. To do this, we are going to remove your first set of training wheels. We are no longer going to be using the CodePens that we've been using before. We are going to use a real developer environment through the Learn IDE.

Training Wheels

The Learn IDE is available as both an in-browser development environment as well as a standalone application.

To choose which environment you would like to work in, on any learn.co page, click your user image in the upper right corner of the page, then click 'Manage Account.'

manage account menu

In Account Management, click 'Learning Environment' and choose either 'IDE In Browser' or 'IDE Download.' Or, if you are already comfortable using an IDE and a console and prefer your own set up, you may also choose 'Local.' This lesson's instructions assume that you are using the Learn IDE in browser.

If you choose 'IDE In Browser' you are set and can navigate back to this lesson. If you have chosen 'IDE Download,' you can download and set up the IDE here.

Now, click "Open IDE" to open your environment. On the left side is your file tree. In the js-from-dom-to-node folder, click index.js to open the file up. IT'S CODING TIME.

Running Code in Chrome's Browser Console

First thing is first, I want to show you that everything we will do in the IDE, you can do in the console. In your browser, right click and select Inspect. Select the Console tab, type console.log("Hello, World!"), and press Enter. You should see "Hello, World!" printed right below your line of code. Congrats! You just wrote your first line of browser-less code. All this does is print out whatever is in between the parenthesis.

Let's bring that code over to our index.js file on the IDE. Make sure you are editing the index.js file, which is inside a folder, js, inside the js-from-dom-to-node folder. Once in there go ahead and paste the following code in there:

console.log('Hello, World!');

Now when you hit Enter, nothing super interesting will happen. All that occurs is the cursor moves to a new line. That's because you are in the text editor. This is pretty much the same as using Word. To get this to actually return something like we did in the Console in the browser we need to execute the index.js file. It sounds super official, but all we are going to do is tell the IDE "I'm ready, run this code and show me the result".

First, we have to save the file. Next, look at the pane at the bottom of the IDE. This is your terminal. Below your code you should see a flashing cursor like this:

command line in ide

Alright, let's let the magic happen! First, we need to make sure we are in the right folder. Our goal is to make it into the "js-from-dom-to-node" folder. If you look at the text next to the time, you should see js-from-dom-to-node or something very similar. If you see that, you are good and you can skip the next section. If it says something else, follow these instructions:

If you see code, we need to go into our labs folder first. To do this type cd labs. Now if should see labs next to the clock. We have to go one more folder in. I know this by looking at the folder structure on the left. See how labs is in code and js-from-dom-to-node is in labs? Ok now we need to cd into the js-from-dom-to-node lab. Take a look at your folder structure on the right to get the exact name and then type cd EXACT-FOLDER-YOU-WANT-TO-ENTER. In my case, I get js-from-dom-to-node. If you were successful, you'll see js-from-dom-to-node next to the clock.

Running Code With Node

To run your code, in your terminal, you can type node index.js. node is the node code runner and index.js is the name of your file. You should see:

Hello, World!

Woot! It worked. You just wrote your first Javascript outside of the browser. Now let's submit it back to Learn. In your terminal type learn submit. This will send your code up to Learn and you may move on to the next lesson.

If you would like to try a few more examples, take a look at the two JavaScript files inside more_js. From your current directory, run node more_js/example_one.js and node more_js/example_two.js to see them in action.

Possible Errors

After you type in node index.js you get something looks like:

    throw err;

Error: Cannot find module '/home/jmburges/code/labs/index.js'
    at Function.Module._resolveFilename (module.js:469:15)
    at Function.Module._load (module.js:417:25)
    at Module.runMain (module.js:604:10)
    at run (bootstrap_node.js:393:7)
    at startup (bootstrap_node.js:150:9)
    at bootstrap_node.js:508:3

The key there is "Error: Cannot find module". That just means you are in the wrong folder. Go back and read the earlier paragraph that starts "If you see code...". That should help you out. You need to be seeing js-from-dom-to-node next to the clock.

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