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CSS

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HTML 

              
                <main class="max-w-6xl mx-auto my-8 pb-4 pl-4 border-l-8 border-l-teal-600">
  <h2 class="text-2xl font-medium text-amber-800">Useful</h2>
  <h1 class="mb-1 text-4xl font-light text-teal-800">Setting Variables w/ <code>style: Bar Chart</code></h1>
  <p class="font-medium">Recently, I came across some HTML code that looked like this: <code>&lt;span style="--w: .5"&gt;...&lt;/span&gt;</code>. "Wow, you can use variabls in a style attribute?!?" In this pen, I experiment with using this method of updating an element's style to produce a horizontal bar chart.</p>
  
  <nav class="dataset-nav mt-12 my-1 mx-12 flex items-center gap-4">    
  </nav>
  <div class="histogram mb-12 mx-12 p-4 border border-slate-500 rounded">
    <div class="title flex flex-col md:flex-row">
      <span class="font-bold text-teal-600 flex-1">Selected Favorite Vegetables<sup><a href="#source" title="Source for the data">1</a></span>
      <span class="current-dataset font-bold">
        All Adults
      </span>
      <nav class="dataset-nav inline-flex items-center">
      </nav>
    </div>
    <div class="graph mt-6">
      <div class="gridset y-axis">
        <div class="col-start-2 col-span-12 pb-1">Popularity: Percent of people who have a positive opintion of the vegetable</div>
      </div>
      
      <div class="gridset series">
        <div class="series-label col-start-1">Potatoes</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: crimson; --w: 90%">
            <span class="sr-only">90% enjoy potatoes</span>              
          </span>
          <span class="percent" aria-hidden="true">90%</span>
        </div>        
      </div>
      
      <div class="gridset series">
        <div class="series-label col-start-1">Sweetcorn</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: plum; --w: 83%">
            <span class="sr-only">83% enjoy sweetcorn</span>             
          </span>
          <span class="percent" aria-hidden="true">83%</span>
        </div>
      </div>
      
      <div class="gridset series">
        <div class="series-label col-start-1">Carrots</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: indigo; --w: 81%">
            <span class="sr-only">81% enjoy carrots</span>
          </span>
          <span class="percent" aria-hidden="true">81%</span>
        </div>      
      </div>
      
      <div class="gridset series">
        <div class="series-label col-start-1">Cucumbers</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: coral; --w: 78%">
            <span class="sr-only">78% enjoy cucumbers</span>
          </span>
          <span class="percent" aria-hidden="true">78%</span>
        </div>      
      </div>
      
      <div class="gridset series">
        <div class="series-label col-start-1">Spinach</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: turquoise; --w: 74%">
            <span class="sr-only">74% enjoy spinach</span>
          </span>
          <span class="percent" aria-hidden="true">74%</span>
        </div>   
      </div>

      <div class="gridset series">
        <div class="series-label col-start-1">Asparagus</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: darkseagreen; --w: 70%">
            <span class="sr-only">70% enjoy asparagus</span>
          </span>
          <span class="percent" aria-hidden="true">70%</span>
        </div>   
      </div>

      <div class="gridset series">
        <div class="series-label col-start-1">Celery</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: goldenrod; --w: 69%">
            <span class="sr-only">69% enjoy celery</span>
          </span>
          <span class="percent" aria-hidden="true">69%</span>
        </div>   
      </div>

      <div class="gridset series">
        <div class="series-label col-start-1">Cauliflower</div>
        <div class="series-data col-span-11">
          <span class="data" style="--c: hotpink; --w: 63%">
            <span class="sr-only">63% enjoy cauliflower</span>
          </span>
          <span class="percent" aria-hidden="true">63%</span>
        </div>   
      </div>

         



    </div>

  </div>
  <div id="source" class="my-12">
    <div class="font-bold">Data Source</div>
    <div><a href="https://today.yougov.com/ratings/consumer/popularity/vegetables/all" target="_blank">"The Most Popular Vegetables (Q12025)" (YouGov | US)</div>
  </div>
</main>
!

CSS 

              
                @import url('https://fonts.googleapis.com/css2?family=Lato:wght@100;300;400;700;900&display=swap');
html, body {
  font-family: "Lato", sans-serif;
  font-size: 20px;
}

.dataset-nav {
  button {
    padding: 0.2rem 0.5rem;
    border: solid 1px LightSlateGray;
    border-radius: 0.5rem;
    &.active {
      border-color: RosyBrown;
      background-color: Beige;
    }
  }
}

.histogram {
  --axis-border: solid 2px LightSlateGray;
  
  position: relative;
  z-index: 0;
  
  .y-axis {
    border-bottom: var(--axis-border);
  }
  .gridset {
    display: grid;
    grid-template-columns: repeat(12, minmax(0, 1fr));
  }
  .series-label {
    border-right: var(--axis-border);   
    font-size: 0.8rem;
  }
  .series-data {
    position: relative;
    margin: 0.2rem;
  }
  .data {
    display: inline-block;
    width: calc(var(--w, 0) - 3rem);
    height: 100%;
    background-color: var(--c, gray);
  }
  .percent {
    display: inline-block;
    font-size: 0.9rem;
    color: SlateGray;
    transform: translateY(-0.3rem);
  }
  
  
}
!

JS 

              
                const datasets = [ 
  {key: 'overall', label: 'All Adults'},
  {key: 'mill', label: 'Millennials'},
  {key: 'genX', label: 'Generation X'},
  {key: 'baby', label: 'Baby Boomers'},
];
let current = datasets[0];

const data = [
  { label: 'Potatoes', 
   overall: .9, mill: .87, genX: .92, baby: .93
  },
  { label: 'Sweetcorn', 
   overall: .83, mill: .8, genX: .9, baby: .90
  },
  { label: 'Carrots', 
   overall: .81, mill: .83, genX: .81, baby: .88
  },
  { label: 'Cucumbers', 
   overall: .78, mill: .78, genX: .77, baby: .79
  },
  { label: 'Spinach', 
   overall: .74, mill: .73, genX: .74, baby: .78
  },
  { label: 'Asparagus', 
   overall: .7, mill: .73, genX: .66, baby: .72
  },
  { label: 'Celery', 
   overall: .69, mill: .67, genX: .66, baby: .75
  },
  { label: 'Cauliflower', 
   overall: .63, mill: .63, genX: .62, baby: .68
  },

];

const colors = ['crimson', 'plum', 'indigo', 'coral', 'turquoise', 'darkseagreen', 'goldenrod', 'hotpink'];


function updateSeries(element, label, percent, color) {
  percent = Math.round(percent < 1 ? percent * 100 : percent);
  const el = {
    label: element.querySelector('.series-label'),
    data: element.querySelector('.series-data .data'), 
    percent: element.querySelector('.series-data .percent'), 
  }
  
  el.label.textContent = label;
  el.data.style.setProperty('--c', color);
  el.data.style.setProperty('--w', `${percent}%`);
  el.data.innerHTML = `<span class="sr-only>${percent}% enjoy ${label}</span>"`;
  el.percent.textContent = `${percent}%`;
}

function updateGraph(key) {
  //sort a clone of the data
  const sorted = [...data.map(m => { return {...m}; })];
  sorted.sort((a,b) => b[key] - a[key]);
  
  const histogram = document.querySelector('.histogram');
  const elements = Array.from(histogram.querySelectorAll('.series'));
  for (let index=0; index<elements.length; index++) {
    const element = elements[index];
    const label = data[index].label;
    const percent = sorted.find(m => m.label === label)[key];
    const colorIndex = sorted.findIndex(m => m.label === label);
    const color = colors[colorIndex];
    
    console.log(">>>", index, {element, label, percent, colorIndex, color});
    
    //verify that the series label matches the data label
    const seriesLabel = element.querySelector('.series-label');
    const seriesData = element.querySelector('.series-data');
    if (seriesLabel?.textContent !== label || !seriesData) {
      console.warn("Unexpected series", {expected: label, found: seriesLabel.textContent});
      throw new Error("Cannot update graph");
    }
    
    updateSeries(element, label, percent, color);    
  }
}

// setup the dataset navigation buttons and their handlers //

function setupDatasetNav() {
  const el = document.querySelector('.dataset-nav');
  //clear
  while (el.firstChild) {
    el.removeChild(el.firstChild);
  }
  
  //create the label:
  const span = document.createElement('span');
  span.className = 'font-bold text-slate-500';
  span.textContent = "Pick a dataset:";
  el.appendChild(span);
  
  //create the buttons
  datasets.forEach(ds => {
    const btn = document.createElement('button');
    btn.textContent = ds.label;
    btn.dataset.key = ds.key;
    btn.addEventListener('click', () => handleDatasetChange(ds.key));
    el.appendChild(btn);
  });

  //update with current nav
  updateDatasetNav();
}

function updateDatasetNav() {
  const el = document.querySelector('.dataset-nav');   
  const buttons = Array.from(el.querySelectorAll('button'));
  buttons.forEach(b => {
    b.classList.toggle('active', b.dataset.key === current.key);
  });
}
function handleDatasetChange(key) {
  const dset = datasets.find(m => m.key === key);
  if (dset) { 
    current = dset;
    updateDatasetNav();
    updateGraph(dset.key);
  }
}

setupDatasetNav();
!
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