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My JavaScript Practice

This directory is for codes that consist of pure HTML, CSS and JavaScript

List

Dove's Step 1 (2022.01.13)

  • Done

    • Generate random footprints on HTML Canvas
    • Draw the canvas' edges rounded with border-radius in CSS
    • Get position (x, y) on canvas that is located relatively
    • Draw footprints in detail with trigonometric function

  • To-be

    • Draw random footprints on HTML Canvas (done)
    • Draw them more naturally with angle and speed
    • Make them disappear gradually like ont the natural snowfield

  • Codes and Results
    Dove's Step 1

    DoveStep.html 
    <!doctype html>

<html lang="en">

    <head>

        <meta charset="utf-8">

        <title>Dove Step Simulation</title>
        <meta name="author" content="kimpro82">

        <link rel="stylesheet" href="DoveStep.css">
        <script defer src="DoveStep.js"></script>

    </head>

    <body>

        <p id="title">Dove's Step Simulation</p>

        <canvas id="canvas" width=600 height=600></canvas>
        <!-- It is necessary to fill width and height in HTML for dealing it with js -->

    </body>

</html>
    DoveStep.css 
    body
{
    text-align: center;
    font-size: 10px;
}
    #title
{
    margin-top: 8rem;
    font-size: 4.5rem;
    margin-bottom: 1rem;

    font-family: Brush Script MT, Georgia, Garamond, Times New Roman, serif;

    color: crimson;
    text-shadow: 0.2rem 0.2rem 0.5rem black;
}
    #canvas
{
    width: 600px;
    height: 600px;

    background-color: white;

    border: 1px solid gray;
    border-radius: 40px;

    box-shadow: 0.2rem 0.2rem 0.5rem;
}
    DoveStep.js 
    // Declare global variables
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
var x = -1, y = -1, direction = 0, step = 0;
var interval = 1000;
    // Start with a click on the canvas
canvas.onclick = function(event)
{
    x = event.clientX - ctx.canvas.offsetLeft;
    y = event.clientY - ctx.canvas.offsetTop;
    // test
    console.log("click point :", x, y);

    footPrint();
}
    // Determine where the next step is located
function randomWalk()
{
    if (x >= 0)
    {
        if (step > 19)
        {
            alert("The dove has archieved " + step + " steps. It became a budda and flied away!");
            return -1;
        }
        else
        {
            x = Math.round(Math.random() * 560) + 20;
            y = Math.round(Math.random() * 560) + 20;
            direction = Math.floor(Math.random() * 360);    // 0 ~ 359

            footPrint();
        }
    }
}
    // Figure the foot print in detail
function footPrint()
{
    var angles = [45, 90, 135, 270];
    ctx.beginPath();
    for (let i = 0; i < 4; i++)
    {
        ctx.moveTo(x, y);
        var x2 = x - Math.round(Math.cos(Math.PI * (angles[i] + direction) / 180) * 20);
        var y2 = y - Math.round(Math.sin(Math.PI * (angles[i] + direction) / 180) * 20);
        ctx.lineTo(x2, y2);
    }
    ctx.closePath();
    ctx.stroke();

    step++;

    // test
    console.log(step + "th step :", x, y, direction);
}
    // Loop by setInterval()
setInterval(randomWalk, interval);
    DoveStepTest.js 
    // Rounding off in JavaScript

console.log(Math.floor(0.7))                // 0
console.log(Math.ceil(1.3))                 // 2
console.log(Math.round(2.3))                // 2
console.log(Math.round(2.7))                // 3
    // Trigonometric Function in JavaScript

console.log(Math.PI);                       // 3.141592653589793
console.log(Math.PI / 180)                  // 0.017453292519943295

console.log(Math.sin(Math.PI / 180))        // 0.01745240643728351
console.log(Math.cos(Math.PI / 180))        // 0.9998476951563913

console.log(Math.sin(Math.PI *   0 / 180))  // 0
console.log(Math.sin(Math.PI *  30 / 180))  // 0.49999999999999994
console.log(Math.sin(Math.PI *  45 / 180))  // 0.7071067811865475
console.log(Math.sin(Math.PI *  60 / 180))  // 0.8660254037844386
console.log(Math.sin(Math.PI *  90 / 180))  // 1
console.log(Math.sin(Math.PI * 180 / 180))  // 1.2246467991473532e-16 ≒ 0
console.log(Math.sin(Math.PI * 270 / 180))  // -1
console.log(Math.sin(Math.PI * 360 / 180))  // -2.4492935982947064e-16 ≒ 0

console.log(Math.cos(Math.PI *   0 / 180))  // 1
console.log(Math.cos(Math.PI *  30 / 180))  // 0.8660254037844387
console.log(Math.cos(Math.PI *  45 / 180))  // 0.7071067811865476
console.log(Math.cos(Math.PI *  60 / 180))  // 0.5000000000000001
console.log(Math.cos(Math.PI *  90 / 180))  // 6.123233995736766e-17 ≒ 0
console.log(Math.cos(Math.PI * 180 / 180))  // -1
console.log(Math.cos(Math.PI * 270 / 180))  // -1.8369701987210297e-16 ≒ 0
console.log(Math.cos(Math.PI * 360 / 180))  // 1

Script Tag's Location (2022.01.02)

  • A topic suggested from my friend Alibaba
  • Compare the results from where the script tag is located
  • Arrange script tag into the head with external .js file link and don't forget the option defer

Codes and Results

  • Case 1. Script tag in the Head Script tag in the Head

    ScriptInHTML_Head.html 
    ……
    <head>

        <meta charset="EUC-KR">
        <title>Script in the Head</title>
        <link rel="stylesheet" href="ScriptInHTML.css">
        <script>document.getElementsByTagName('p')[0].style.color = "red"</script>

    </head>
……
    ScriptInHTML_Head.css 
    p {
  text-align: center;
  font-family: Brush Script MT, Georgia, Garamond, Times New Roman, serif;
  /* font reference ☞ https://www.w3schools.com/css/css_font.asp */
    color: blue;
  font-size: 700%;
  margin: 0;
}

  • Case 2. Script tag in the Bottom of the Body Script tag in the Bottom of the Body

    ScriptInHTML_BodyEnd.html 
    ……
    <body>

        <p>Be the reads!</p>
        <script>document.getElementsByTagName('p')[0].style.color = "red"</script>

    </body>
……

  • Case 3. Script tag with defer option Script tag in the External .js file

    ScriptWithDefer.html 
    ……
    <head>

        ……
        <script defer src="ScriptWithDefer.js"></script>
        <!-- don't forget "defer" ! -->

    </head>
……
    ScriptWithDefer.js 
    document.getElementsByTagName('p')[0].style.color = "red"

Colorful Show (2020.03.04)

  • This is a colorful 'Show'

    Colorful Show

    ColorfulShow.html 
    <!DOCTYPE html>

<html>

<head>
  <meta charset="EUC-KR">
  <title>Colorful Show</title>
    <link rel="stylesheet" href="ColorfulShow.css">
</head>

<body>
  <p id='chameleon'>Show</p>
    <script src="ColorfulShow.js">
    <!--
      <script> can be located in <head> or <body>. 
      But, in this case, we should consider execution sequence.
    -->
    
  </script> 
</body>

</html>
    ColorfulShow.css 
    @charset "EUC-KR";

#chameleon {
  text-align: center;
  font-family: "Times New Roman", Times, serif;
  font-size: 1000%;
}
    ColorfulShow.js 
    function changeColor() {
  randNumDec = Math.floor(Math.random() * Math.pow(256, 3));
    /*
    * Math.random() returns a number lower than 1.
    * Math.floor() returns the largest integer less than or equal to a given number.
    * 256**3 is for the RGB color range between #000000 ~ #FFFFFF.
    */
  randNumHex = randNumDec.toString(16); /* Convert Decimal to Hexadecimal */

  /* document.write(randNumHex, "<br>"); */
    /* document.write() returns real HTML codes. */
    /* document.write(typeof randColor);
    * string
    */

  document.getElementById('chameleon').style.color = '#' + randNumHex;
}

setInterval(changeColor, 1000);

Ganzi (2017.04.03)

  • A simple Javascript practice

    Ganzi

    Ganzi.html 
    <div id ="Zure">Ganzi</div>

<script type="text/javascript">
  
function thunder() {
  var x = document.getElementById("Zure");
  var storm = document.write(x.innerHTML + " Storm");
  Zure.replace(x,storm);
}
setInterval(thunder, 3000);
  
</script>