Category: Javascript

Vue.js Studies Day 6 – Beyond “Getting Started”

The previous post to this one, just included some definitions to ensure I’ve covered the core topics as I’m moving along. Before that I covered getting a project app started in day 3 and day 2 posts. Before that I covered the curriculum flow I’m covering in these studies.

Now that I’ve covered a number of ways to get started with a Vue project with; JetBrains WebStorm, hand crafted artisanal, or via NPM it’s time to start covering the basics of how to build an app using Vue.js. I’ll be using the WebStorm IDE for development but will still call out where or what I’d need to do if I were working from the terminal with something else. By using the WebStorm IDE, I’ll also be starting from the generated app that the IDE created for me.

main.js

Starting in the src directory of the project, let’s cover a few of the key parts of this project of the application as created. First, we have a main.js file. In that file is the following code. This little bit of code is what is responsible for working with the Virtual DOM to mount the application to it for rendering the page we eventually see.

import { createApp } from 'vue'
import App from './App.vue'

import './assets/main.css'

createApp(App).mount('#app')

The first two lines import two variables from the ‘vue’ library called createApp and create an App object from ‘./App.vue’ template. Then the third import is just pulling in the main.css file. The fourth line uses the createApp operatig on the App object to .mount the application at the point of the #app anchor in the template App.vue. That leads to needing to take a look at App.vue to see what exactly the vue app is mounted to.

NOTE: I’m not 100% sure I’m describing this as precisely as I should, as the blog entry details, this is day 4 of Vue.js studies. I’d started in the past once or twice, and have done a ton of web dev over the years, but Vue.js is largely new to me. So if you see something worded incorrectly or oddly, please comment with questions or corrections.

App.vue

The App.vue file for the WebStorm generation seems to have a bit more from the other apps generated from other tooling. Whatever the case, let’s pick this apart and learn what is which and which is what in this file.

<script setup>
import HelloWorld from './components/HelloWorld.vue'
import TheWelcome from './components/TheWelcome.vue'
</script>

<template>
  <header>
    <img alt="Vue logo" class="logo" src="./assets/logo.svg" width="125" height="125" />

    <div class="wrapper">
      <HelloWorld msg="You did it!" />
    </div>
  </header>

  <main>
    <TheWelcome />
  </main>
</template>

<style scoped>
header {
  line-height: 1.5;
}

.logo {
  display: block;
  margin: 0 auto 2rem;
}

@media (min-width: 1024px) {
  header {
    display: flex;
    place-items: center;
    padding-right: calc(var(--section-gap) / 2);
  }

  .logo {
    margin: 0 2rem 0 0;
  }

  header .wrapper {
    display: flex;
    place-items: flex-start;
    flex-wrap: wrap;
  }
}
</style>

Right at the beginning of the App.vue file there is a <script setup></script> section that imports two other components that are located in the components directory that the App.vue file is located in. This is the HellowWorld.vue and TheWelcome.vue components. There is a third component, the WelcomeItem.vue component, in the component directory along with an icons directory.

With all of these assets now ready, clicking on the play or debug buttons in WebStorm will issue to the command to execute and display the app in the default browser. I’ll cover more of the assets as we get to each of them, for now I’m going to move along and get into some components and all.

When the IDE (or you do manually) launches the browser to display the app it will look like this.

Checkpoint: Vue App Operational

This is a good time to checkpoint. If you’ve been following along and everything is as shown above, we’re good to move along to the next steps. If not, then something is amiss, probably broken, and that needs resolved first. If you’ve run into a problem at this point, leave a comment with a description of the issue and I’ll endeavor to help you resolve the problem. Otherwise, moving along to some edits and checking out Vue.js’s features and capabilities.

Once the next post is live, I’ll add the link here to that post… it’s coming soon!

Day 5 Studies – Linked Lists 😱

I needed a refresher, as I’m at the point in my career I tend to just implement the things and not remember what they’re called anymore. Whether a refresher or you’re new to coding, maybe my refresher will be a good stroll through linked lists.

First off, what exactly is a linked list? The name sort of defines what we’re talking about, but a definition would definitely help. From an actual dictionary, I dug up the following definition.

“A simple linear data structure, each of whose nodes includes a pointer to the next (and sometimes previous) node in the list, enabling traversal of the structure in at least one direction from any starting point.”

via Wordnick

The parenthesis above overloads the definition a bit in describing both a simple linked list and a doubly linked list. Let’s define further to differentiate those two and throw in a circular one to boot.

Singly Linked Lists

Each node contains a pointer to the next node. The code for a singly linked list would look something like this, if you put it together in JavaScript.

class ListNode {
    constructor(data) {
        this.data = data
        this.next = null
    }
}

class LinkedList {
    constructor(head = null) {
        this.head = head
    }
}

Note however, in this example, the pointer is really the next inferred object. You’d need to use a language like C, or C++, to build a linked list with an actual pointer. that would look something like this.

struct Node {
    int data;
    struct Node* next;
};

#include <bits/stdc++.h>
using namespace std;
 
class Node {
public:
    int data;
    Node* next;
};
 
void printList(Node* n)
{
    while (n != NULL) {
        cout << n->data << " ";
        n = n->next;
    }
}

Here you can see the * used to set a pointer and then the reference to move between the nodes below. It’s a bit more complicated using a language like this, but I wanted to – because I’m often complicated – point out how it would be done with C++. This introduces additional capabilities, but I won’t go on about the nuances of using actual pointers here and am instead going to focus on the linked list concepts themselves. However it doesn’t hurt to know this and along with pointers themselves, this is a great topic for another post another time, so back to linked lists!

Referring back to the JavaScript example above, if you were to build out several nodes like this.

let node1 = new ListNode("a singular node.")
let node2 = new ListNode("some other node.")
let node3 = new ListNode("and another rando node.")

Then put together the nodes, and instantiate a linked list like this.

node1.next = node2
node2.next = node3

let list = new LinkedList(node1)

You can then request various nodes of the linked list or get the linked list object itself like this.

console.log(list.head)  
console.log(list.head.next.data)
console.log(list.head.next.next.data)

The first console log would print out the entire list.head object, which means all of the nested objects too. That would look like this.

ListNode {
  data: 'a singular node.',
  next: ListNode {
    data: 'some other node.',
    next: ListNode { data: 'and another rando node.', next: null }
  }
}

The second and third console logs would print out "some other node." and "and another rando node." respectively.

Double Linked Lists

Each node contains a pointer to the next and previous nodes. That turns the above example into this.

class ListNode {
    constructor(data) {
        this.data = data
        this.next = null
        this.prev = null
    }
}

class LinkedList {
    constructor(head = null) {
        this.head = head
    }
}

Summary

That’s the short SITREP on LinkedLists. There’s a lot more to cover, the functions that work on the list, the traversals, the addition and removal of nodes, etc. But this post is just intended for a quick review of the structure of linked lists at their core. On to next topics, cheers!

Could not resolve “@popperjs/core”

I keep getting this error on running dev. Albeit it doesn’t appear I’m getting it in production.

I run.

npm run dev

Then everything appears to be ok, with the standard message like this from vite.

  vite v2.9.9 dev server running at:

  > Local: http://localhost:3000/
  > Network: use `--host` to expose

  ready in 740ms.

But then, once I navigate to the site to check things out.

X [ERROR] Could not resolve "@popperjs/core"

    node_modules/bootstrap/dist/js/bootstrap.esm.js:6:24:
      6 │ import * as Popper from '@popperjs/core';
        ╵                         ~~~~~~~~~~~~~~~~

  You can mark the path "@popperjs/core" as external to exclude it from the bundle, which will
  remove this error.

…and this error annoyingly crops up.

11:36:23 PM [vite] error while updating dependencies:
Error: Build failed with 1 error:
node_modules/bootstrap/dist/js/bootstrap.esm.js:6:24: ERROR: Could not resolve "@popperjs/core"
    at failureErrorWithLog (C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:1603:15)
    at C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:1249:28
    at runOnEndCallbacks (C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:1034:63)
    at buildResponseToResult (C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:1247:7)
    at C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:1356:14
    at C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:666:9
    at handleIncomingPacket (C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:763:9)
    at Socket.readFromStdout (C:\Users\Adron Hall\Codez\estuary\node_modules\esbuild\lib\main.js:632:7)
    at Socket.emit (events.js:315:20)
    at addChunk (_stream_readable.js:309:12)
Vite Error, /node_modules/.vite/deps/pinia.js?v=72977742 optimized info should be defined
Vite Error, /node_modules/.vite/deps/bootstrap.js?v=14c3224a optimized info should be defined
Vite Error, /node_modules/.vite/deps/pinia.js?v=72977742 optimized info should be defined
Vite Error, /node_modules/.vite/deps/pinia.js?v=72977742 optimized info should be defined (x2)

...

…and on and on and on goes these errors. For whatever reason, even though npm install has been run once just get to the point of running npm run dev, there needs to be a subsequent, specifically executed npm install @popperjs/core to install this particular dependency that throws this error.

So that’s it, that’s your fix. Cheers!

The Best Collected Details on the GraphQL Specification, Section 3

References https://spec.graphql.org specifically October 2021 Edition.

This is the second part (the first part covered the overview and language of GraphQL) to a collection of notes and details, think of this as the cliff notes of the GraphQL Spec. Onward to section 3 of the spec…

The GraphQL type system is described in section 3 of the specification. Per the specification itself,

The GraphQl Type system describes the capabilities of a GraphQL service and is used to determine if a requested operation is valid, to guarantee the type of response results, and describes the input types of variables to determine if values provided at request time are valid.

This feature of the specification for the GraphQL language uses Interface Definition Language (IDL) to describe the type system. This can be used by tools to provide utility function as client code genration or boot-strapping. In a lot of the services and products around GraphQL like AppSync, Hasura, and others you’ll see this specifically in action. Tools that only execute requests can only allow TypeSystemDocument and disallow ExecuteDefintion or TypeSystemExtension to prevent extensions of the type system. If you do this be sure to provide a descriptive error for consumers of your data!

Continue reading “The Best Collected Details on the GraphQL Specification, Section 3” →

A Shiny New Vuejs v3 Web App Using & Deployed to Amplify/AppSync/Cognito

No cruft, let’s just start.

Continue reading “A Shiny New Vuejs v3 Web App Using & Deployed to Amplify/AppSync/Cognito” →