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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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Adding Classes

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About the <head>

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Insecure Resource

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CSS

About CSS Preprocessors

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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You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.

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Packages

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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 

              
                <br />
<p>
<center>
<a href="#">Rainbow Hover Color</a>
</center>
</p>
!

CSS 

              
                html{
  background-color:#333;
  color:#fff;
  overflow-x:hidden;
}
a{
  text-decoration:none;
  font-size:30px;
  color:#fff;
}
!

JS 

              
                // <![CDATA[
/* Setting */
/* Increase amount(The degree of the transmutation) */
var rate = 20;
/* Main routine */
if (document.getElementById)
window.onerror=new Function("return true")
/* The object which event occured in */
var objActive;
/* Flag during the action */
var act = 0;
/* Hue */
var elmH = 0;
/* Saturation */
var elmS = 128;
/* Value */
var elmV = 255;
/* A color before the change */
var clrOrg;
/* Timer ID */
var TimerID; 
/* ---------- */
if (document.all) {
    document.onmouseover = doRainbowAnchor;
    document.onmouseout = stopRainbowAnchor;
}
else if (document.getElementById) {
    document.captureEvents(Event.MOUSEOVER | Event.MOUSEOUT);
    document.onmouseover = Mozilla_doRainbowAnchor;
    document.onmouseout = Mozilla_stopRainbowAnchor;
}
/* doRainbow Function begins to change a color */
function doRainbow(obj)
{
    if (act == 0) {
        act = 1;
        if (obj)
            objActive = obj;
        else
            objActive = event.srcElement;
        clrOrg = objActive.style.color;
        TimerID = setInterval("ChangeColor()",100);
    }
}
/* stopRainbow Function stops to change a color */
function stopRainbow()
{
    if (act) {
        objActive.style.color = clrOrg;
        clearInterval(TimerID);
        act = 0;
    }
}
/* doRainbowAnchor Function begins to change a color */
/* (of a anchor, automatically) */
function doRainbowAnchor()
{
    if (act == 0) {
        var obj = event.srcElement;
        while (obj.tagName != 'A' && obj.tagName != 'BODY') {
            obj = obj.parentElement;
            if (obj.tagName == 'A' || obj.tagName == 'BODY')
                break;
        }

        if (obj.tagName == 'A' && obj.href != '') {
            objActive = obj;
            act = 1;
            clrOrg = objActive.style.color;
            TimerID = setInterval("ChangeColor()",100);
        }
    }
}
/* stopRainbowAnchor Function stops to change a color */
/* (of a anchor, automatically) */
function stopRainbowAnchor()
{
    if (act) {
        if (objActive.tagName == 'A') {
            objActive.style.color = clrOrg;
            clearInterval(TimerID);
            act = 0;
        }
    }
}
/* Mozilla_doRainbowAnchor(for Netscape6 and Mozilla browser) */
/* This function begins to change a color. (of a anchor, automatically) */
function Mozilla_doRainbowAnchor(e)
{
    if (act == 0) {
        obj = e.target;
        while (obj.nodeName != 'A' && obj.nodeName != 'BODY') {
            obj = obj.parentNode;
            if (obj.nodeName == 'A' || obj.nodeName == 'BODY')
                break;
        }

        if (obj.nodeName == 'A' && obj.href != '') {
            objActive = obj;
            act = 1;
            clrOrg = obj.style.color;
            TimerID = setInterval("ChangeColor()",100);
        }
    }
}
/* Mozilla_stopRainbowAnchor(for Netscape6 and Mozilla browser) */
/* This function stops to change a color. (of a anchor, automatically) */
function Mozilla_stopRainbowAnchor(e)
{
    if (act) {
        if (objActive.nodeName == 'A') {
            objActive.style.color = clrOrg;
            clearInterval(TimerID);
            act = 0;
        }
    }
}
/* Change Color This function changes a color actually */
function ChangeColor()
{
    objActive.style.color = makeColor();
}
/* makeColor This function makes rainbow colors */
function makeColor()
{
/*Don't you think Color Gamut to look like Rainbow?*/
/* HSVtoRGB */
    if (elmS == 0) {
        elmR = elmV;    elmG = elmV;    elmB = elmV;
    }
    else {
        t1 = elmV;
        t2 = (255 - elmS) * elmV / 255;
        t3 = elmH % 60;
        t3 = (t1 - t2) * t3 / 60;

        if (elmH < 60) {
            elmR = t1;  elmB = t2;  elmG = t2 + t3;
        }
        else if (elmH < 120) {
            elmG = t1;  elmB = t2;  elmR = t1 - t3;
        }
        else if (elmH < 180) {
            elmG = t1;  elmR = t2;  elmB = t2 + t3;
        }
        else if (elmH < 240) {
            elmB = t1;  elmR = t2;  elmG = t1 - t3;
        }
        else if (elmH < 300) {
            elmB = t1;  elmG = t2;  elmR = t2 + t3;
        }
        else if (elmH < 360) {
            elmR = t1;  elmG = t2;  elmB = t1 - t3;
        }
        else {
            elmR = 0;   elmG = 0;   elmB = 0;
        }
    }

    elmR = Math.floor(elmR).toString(16);
    elmG = Math.floor(elmG).toString(16);
    elmB = Math.floor(elmB).toString(16);
    if (elmR.length == 1)    elmR = "0" + elmR;
    if (elmG.length == 1)    elmG = "0" + elmG;
    if (elmB.length == 1)    elmB = "0" + elmB;

    elmH = elmH + rate;
    if (elmH >= 360)
        elmH = 0;

    return '#' + elmR + elmG + elmB;
}
// ]]>
!
999px

Console