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Today I Learned

Regex simplicity vs normal

There are some cases when making use of regular expressions (regex) can exempt a lot of fuss from a programmers head. For example, let's compare the complexity between traditional logic and regex, in a function that excludes the vowels from a given string:

Traditional way:

function removeVowel(str) {
  let strList = str.split('');
  for (let i = 0; i < str.length; i++) {
    let char = str[i].toLowerCase();
    if (char == "a" || char == "e" || char == "i" || char == "o" || char == "u") {
      strList[i] = '';
    }
  }
  return strList.join('');
}

Regex Way:

function removeVowel(str){
  return str.replace( /[aeiou]/ig, '')
}

Temporarily render empty container until image is loaded to the screen

If we have a component that contains an image or video, we may face the case in which the component takes a different size from the one that is expected in the loading phase. This is because, while the image is loading, the size of the image is unknown, therefore the component will not render the image initially. This topic will throw a lot of issues and it can affect the user experience in a negative way, because components may take unnatural shapes while in the loading process.

This problem can be overcome by temporarily rendering:

  • an empty container with the estimated photo dimensions
  • a low resolution preview of the photo
  • a default blurred image that will show the user what to expect from the UI

In the case we want to temporarily render a empty div to the screen, we may need to mimic a responsive feel to the box, therefore "calc()" CSS function may come in handy:

.empty-div {
     background-color: transparent;
     background-size: 100% auto;
     width: calc(100vw - 100px);
     height: calc((100vw - 100px) * 0.46); /* decimal = height aspect ratio */
}

Add event listener on page resize

There is a special event listener in javascript that is called whenever a page resize is detected. The event listener is named 'resize' and can be used in the following way:

function onFrameResize(){
  console.table(
    {
      Height: window.innerHeight,
      Width: window.innerWidth  
    }
  );
}

window.addEventListener("resize", onFrameResize);

"window.innerHeight" and "window.innerWidth" are functions to access the width and the height of the frame.

This functionality will come in handy when working with responsive components.

Call function when image is loaded in VueJS using @load.

In VueJS, there is a way to find out when an image is fully loaded on a web page (when the image request is finished). We achieve this using the @load event that is available in VueJS and works in the following way:

<template>
  <div>
    <img 
      class="img__class"
      src="/photo.jpg"
      @load="onImageLoad"
     />
  </div>
</template>

export default {
  data: {
    isImageLoaded: false,
  },

  methods: {
    onImageLoad() {
      this.isImageLoaded = true
      // optional
      // console.log('Image is loaded')
    }
  }
}

This feature will come in handy if we want to render skeleton components while images are loading or if we want to implement lazy loading functionality.

How to dynamically render components in "vue-infinite-loading" using relative heights

When working with an infinite loading library like "vue-infinite-loading" or "vue-infinite-scroll", instead of hardcoding the amount of components to be rendered per page, we might use a technique to estimate the right number, based on the height of the browser window and the height of the component.

We need to obtain both of those heights and then divide them to obtain the number we are looking for. First, we can obtain the height of the browser window by using the following command:

window.innerHeight

After that, in order to obtain the height of the components rendered in the infinite scroll window, we may use:

this.$refs.yourComponentRefHere.clientHeight

"clientHeight" will return the height of the component and now, we can divide the numbers obtained to get the render number. ( Note: as a safety measure, the number we get should be larger than the obtained number, therefore we need to add a number to it to be sure it will behave as desired).

By using this technique we can change the render number in a responsive manner and can avoid unnecessary requests in order to give the user a more performant user experience.

Note: We can also dynamically adjust the render number if the window size changes, by adding a watcher and the following event listener:

window.addEventListener('resize',onResize)

Where "onResize" is the action to re-calculate the render number.

Visual Studio Code Snippets

VS Code offers the possibility to create personalized code snippets. These Code snippets can be configured for a specific user, globally, for a certain project or programming language.

For example, if a user wants to avoid the repetitive writing of the basic "console.log({})", after configuring the snippets, it will be enough to write a prefix like: "cl" or "log" and VSC will autocomplete the code snippet. The braces {} will also show the variable name before the result.

In order to achieve this, we can run the command "Preferences: Configure User Snippets" in VSC and a popup will appear showing the types of of snippets to configure.

If we wish to configure a snippet as in the 'console.log' example above, we need to choose to modify the "javascript.json" file with the following content:

{
    "Print to console": {
        "prefix": "cl",
        "body": [
	    "console.log({$1});",
	    "$2"
	],
        "description": "Log output to console"
	}
}

As you can see, a certain snippet will have a prefix under it will be accessed, a body (the code that will be inserted) and the description of the snippet.

This is a powerful feature of VSC and can avoid repetitive code writing that can be quite tedious after a while.

More info about this feature of VSC can be found here:

https://code.visualstudio.com/docs/editor/userdefinedsnippets#_create-your-own-snippets

Conditionally loading packages based on environment.

Based on the environment of the project (production or development), there is a way to load packages conditionally. We may want to load packages conditionally to keep an easier to run development server, for instance.

In order to achieve this, we may use the following technique, if the used packages do not already feature a parameter to be used accordingly to the environment.

For instance we may provide an APP_ENVIRONMENT parameter in the .env file of the project. Based on the value of the parameter, we may load or not a package.

.env

APP_ENVIRONMENT=development

nuxt.config.js

let modules = {
  "@nuxtjs/axios",
}

if (process.env.APP_ENVIRONMENT !== "development")
  modules.push("@nuxtjs/component-cache")

Customize web page using query parameters with help of $route.query

VueJS offers the possibility to access query parameters so that you can customise a certain's page content based on the given parameters.

For instance, we have the following method and the following query parameters:

https://*link*?message=Custom+Message
    getQuery() {
      if (this.$route.query.message) {
        this.queryMessage = this.$route.query.message
      }
    },

This method will set a variable according to the query parameter "message", that can be further used in the content of the page. For example in a heading:

    <h1>{{ queryMessage }}</h1>

Also, by using the functionality of $router combined with "v-if", the user can render components conditionally.

    getQuery() {
      if (this.$route.query.icon) {
        this.queryIcon = this.$route.query.icon === 'true'
      }
    },
    <svg v-if="queryIcon">

Therefore, when parsing a query containing:

?icon=true

only then, the svg will be rendered.

Postman Automatic Auth Token

Postman can run JavaScript commands when executing a request. These commands can be placed in the "Tests" tab inside a request. For example, to automatically set a token as a collection variable, the following commands are used:

var auth = pm.response.headers.get("Authorization");
pm.collectionVariables.set('token', auth.split(" ")[1]);

The Docs regarding Postman scripting can be found here:

https://learning.postman.com/docs/writing-scripts/script-references/postman-sandbox-api-reference/