Using CSS selectors within the style attribute

Question

I have a nice little button which uses a lot of fancy CSS to look good.

Here's the code behind it (I'm ignoring compatibility issues for now); as you can see, it uses a few selectors for hover and click events.

.button {
    display: inline-block;
    width: 200px;
    height: 200px;
    padding: 15px;
    border-radius: 25px;
    background:linear-gradient(to bottom, hsla(36, 100%, 60%, 1) 5%, hsla(36, 100%, 40%, 1) 100%);
    border:2px solid hsla(36, 100%, 30%, 1);
    box-shadow:inset 0px 2px 2px 0px white;
    position: relative;
    left: 0px;
    top: 0px;
    text-shadow:0px 1px 0px hsla(36, 100%, 30%, 1);
    margin: 25px;
}

.button:hover {
    background:linear-gradient(to bottom, hsla(36, 100%, 65%, 1) 5%, hsla(36, 100%, 45%, 1) 100%);
}

.button:active {
    background:linear-gradient(to bottom, hsla(36, 100%, 40%, 1) 5%, hsla(36, 100%, 60%, 1) 100%);
}

However, to streamline the process in the future when there will be many buttons, I instead wanted to be able to make the button have a custom attribute for colour ( buttonColor below) which will be read by some JavaScript, turned into Hue/Saturation/Lightness, and eventually changed for the many different variations. Each button contains at least three colours; two for the gradient and one for the drop shadow and border.

<div class="button" id="testButton"buttonColor="ff8c00">
    <p class="buttonHeader">foo</p>
    <p class="buttonBody">foo2</p>
</div>

Here's what I've got in the JavaScript:

function hexToRgb(hex) {  //converts hexadecimal colors into Red/Green/Blue
    //code omitted for sake of conciseness
    return [r, g, b];
}
function rgbToHsl(r, g, b) { //converts Red/Green/Blue into Hue/Saturation/Lightness
    //ditto
    return [h, s, l]
}

var buttons = document.body.getElementsByClassName('button'); //Gets all elements with button class

for (var i = 0; i < buttons.length; i++) {
    var rgb = hexToRgb(buttons[i].getAttribute("buttoncolor")); //
    var hsl = rgbToHsl(rgb.r, rgb.g, rgb.b)
    //here
}

And right there is where I'm stuck.

I can easily modify the style of the button, but only while it's inactive; There's no way I've found to change how it reacts under the :hover and :active selectors.

Answer 1

use data attributes! try something like this:

<div class="button" id="testButton" data-button-color="ff8c00">
    <p class="buttonHeader">foo</p>
    <p class="buttonBody">foo2</p>
</div>

js

function hexToRgb(hex) {
    // Expand shorthand form (e.g. "03F") to full form (e.g. "0033FF")
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function(m, r, g, b) {
        return r + r + g + g + b + b;
    });

    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
}

function rgbToHsl(r, g, b){
    r /= 255, g /= 255, b /= 255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, l = (max + min) / 2;

    if(max == min){
        h = s = 0; // achromatic
    }else{
        var d = max - min;
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
        switch(max){
            case r: h = (g - b) / d + (g < b ? 6 : 0); break;
            case g: h = (b - r) / d + 2; break;
            case b: h = (r - g) / d + 4; break;
        }
        h /= 6;
    }

    return [h, s, l];
}




var buttons = document.body.getElementsByClassName('button'); //Gets all elements with button class

for (var i = 0; i < buttons.length; i++) {
    var rgb = hexToRgb(buttons[i].data("button-color")),
        hsl = rgbToHsl(rgb.r, rgb.g, rgb.b),
        rules = [];
    rules[i][0] = hsl;

    hsl[2] = 100 - hsl[2]; // make second color
    rules[i][1] = hsl;
    var len = rules.length;
    for(;len--;) {
        buttons[i].style = 
            "background: linear-gradient(to bottom, hsla(36, 100%, "+rules[i][0]+"%, 1) 5%, hsla(36, 100%, "+rules[i][1]+"%, 1) 100%);"; // put rules on el
    }
}

edit

David Walsh has an excellent post on adding rules to stylesheets with js .

let's say you made a rules array

var rules = [...]; // ['float: left', 'cursor: pointer']

or object

var rules = {
    'hover': [...], // rules...
    'active': [...]
};

in your code above. You could then insert them with the following:

var sheet = (function() {
    var style = document.createElement("style");
    style.appendChild(document.createTextNode(""));
    document.head.appendChild(style);
    return style.sheet;
})();

function addCSSRule(sheet, selector, rules, index) {
    if("insertRule" in sheet) {
        sheet.insertRule(selector + "{" + rules + "}", index);
    }
    else if("addRule" in sheet) {
        sheet.addRule(selector, rules, index);
    }
}

// ['float: left', 'cursor: pointer']
addCSSRules(document.styleSheets[0], ".button:hover", rules.join(';'));

or

// { 'hover': ['float: left'], 'active': ['cursor: pointer']};
addCSSRules(document.styleSheets[0], ".button:hover", rules.hover.join(';'));
addCSSRules(document.styleSheets[0], ".button:active", rules.active.join(';'));