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HTML

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HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.

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!
Insecure Resource

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CSS

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CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.

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CSS Base

About CSS Base

It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.

Vendor Prefixing

About Vendor Prefixing

To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit- or -moz-.

We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).

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JavaScript

About JavaScript Preprocessors

JavaScript preprocessors can help make authoring JavaScript easier and more convenient.

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Babel includes JSX processing.

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Packages

Add Packages

Search for and use JavaScript packages from npm here. By selecting a package, an import statement will be added to the top of the JavaScript editor for this package.

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Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.

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HTML 

              
                <article>
  <h2>JavaScript String Split</h2>
  <section>
    <aside id="left">
      <p>Syntax</p>
      <ul id="syntax">

      </ul>
    </aside>
    <aside id="right">
      <p>String Split Result From Console</p>
      <ul id="result">

      </ul>
    </aside>
  </section>
</article>
!

CSS 

              
                * {
  text-align: center;
  font-size: 1.15rem;
}
section {
  border: solid 2px black;
  border-radius: 7px;
  margin: auto;
  background-color: #2d3e50;
}
article {
  width: 100%;
  text-align: center;
}
aside {
  margin: 2px;
}
p {
  border: solid 2px black;
  border-radius: 7px;
  background-color: #00bda5;
  margin: 5px;
  padding: 5px;
  color: #2d3e50;
}
#left {
  display: inline-grid;
  width: 25%;
}
#right {
  display: inline-grid;
  width: 65%;
}
ul {
  list-style: none;
  display: block;
  padding: 0px;
  margin: 0px;
}
li {
  border: solid 2px black;
  border-radius: 7px;
  text-align: left;
  color: white;
  margin: 5px;
  padding: 10px;
  background-color: #ff5c35;
}
#left li {
  text-align: center;
}
!

JS 

              
                let intro = "Hello! I'm The Doctor.";

/*Returns
// [object Array] (1)
["Hello! I'm The Doctor."]
*/
let noParams = intro.split();

/*
// [object Array] (2)
["Hello"," I'm The Doctor."]
*/
let atSpecChar = intro.split("!");

/*
[object Array] (22)
["H","e","l","l","o","!"," ","I","'","m"," ","T","h","e"," ","D","o","c","t","o","r","."]
*/
let atEachChar = intro.split("");

/*
[object Array] (5)
["H","e","l","l","o"]
*/
let eachCharMaxFive = intro.split("", 5);

let splitExArray = [noParams, atSpecChar, atEachChar, eachCharMaxFive];
let splitExSyntax = [
  `intro.split()`,
  `intro.split("!")`,
  `intro.split("")`,
  `intro.split("", 5)`
];
for (i = 0; i < splitExArray.length; i++) {
  let exSyntax = document.createElement("LI");
  document.getElementById("syntax").appendChild(exSyntax);
  exSyntax.setAttribute("id", `playerNum${i + 1}`);

  //Create player number text node, then append text node
  let playerNum = document.createTextNode(`${splitExSyntax[i]} `);
  exSyntax.appendChild(playerNum);

  let splitExample = document.createElement("LI");
  document.getElementById("result").appendChild(splitExample);
  splitExample.setAttribute("id", `splitExample${i}`);
  let arrayItems = [];
  for (id = 0; id < splitExArray[i].length; id++) {
    arrayItems.push(`"${splitExArray[i][id]}"`);
  }
  let splitResult = document.createTextNode(`[${arrayItems}]`);
  document.getElementById("result").appendChild(splitExample);
  splitExample.appendChild(splitResult);
  splitExample.setAttribute("id", `noParams`);
}
!
999px

Console