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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

HTML

            
              
            
          
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CSS

            
              html { height: 100%; }
body {
  align-items: center;
  background-color: #1D1E22;
  display: flex;
  justify-content: center;
  height: 100%;
}

svg {
  background-color: #fff;
  padding: 120px 60px 160px 120px;
}

.title {
  font-size: 24px;
}

div.tooltip {
  background: rgba(112, 127, 140, .85);
  border: none;
  border-radius: 2px;
  color: #fff;
  font-size: 18px;
  padding: 10px 20px;
  pointer-events: none;
  position: absolute;
  text-align: center;
  width: 150px;
}

.cell:hover {
  stroke: #333 !important;
  stroke-width: 2px !important;
}
            
          
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JS

            
              // store dat in variable
const dataURI = 'https://raw.githubusercontent.com/freeCodeCamp/ProjectReferenceData/master/global-temperature.json'

// set up svg
const w = 1200
const h = 500
const margin = { top: 30, right: 10, bottom: 30, left: 10 }
const cellSize = 50
const svg = d3.select('body')
              .append('svg')
              .attr('width', w)
              .attr('height', h)

// set up chart title
svg.append('text')
   .attr('transform', `translate(${w/2}, ${margin.top - 100})`)
   .attr('class', 'title')
   .attr('id', 'title')
   .style('text-anchor', 'middle')
   .text('Monthly Global Land-Surface Temperature')

// set up chart subtitle
svg.append('text')
   .attr('transform', `translate(${w/2}, ${margin.top - 70})`)
   .attr('class', 'description')
   .attr('id', 'description')
   .style('text-anchor', 'middle')
   .text('1753 - 2015: base temperature 8.66°C')

// read in data
d3.json(dataURI, { crossOrigin: 'anonymous' }).then(({ monthlyVariance }) => {
  
  // set base temp
  const base = 8.66
  
  // separate data into variables
  const variances = monthlyVariance.map(item => item.variance)
  const temps = monthlyVariance.map(item => base + item.variance)
  const years = monthlyVariance.map(item => item.year)
  
  // set up colors
  const colors = ["#313695", "#4575b4", "#74add1", "#abd9e9", "#e0f3f8", "#ffffbf", "#fee090", "#fdae61", "#f46d43", "#d73027", "#a50026"]
  
  const colorScale = d3.scaleQuantize()
                       .domain(d3.extent(variances))
                       .range(colors)
  
  // set up x scale
  const xScale = d3.scaleLinear()
                   .domain(d3.extent(years))
                   .range([margin.left, w - margin.right])
  
  // set up y scale
  let months = Array.from(Array(13).keys()) // ES6 technique to create N-element array [0, 1, ..., N-1] - https://goo.gl/i6YT7D
  months.shift()
  months = months.map(month => moment(month, 'MM').format('MMMM'))
  
  const yScale = d3.scaleBand()
                   .domain(months.reverse()) // reverse months for yAxis
                   .range([h, 0])
  
  // append div for use as tooltip
  const tooltip = d3.select('body')
                    .append('div')
                    .attr('class', 'tooltip')
                    .attr('id', 'tooltip')
                    .style('opacity', 0)
  
  // reverse months back to normal
  months.reverse()
  
  // set up heat map cells
  svg.selectAll('rect')
     .data(monthlyVariance)
     .enter()
     .append('rect')
     .attr('x', d => xScale(d.year))
     .attr('y', d => (d.month - 1) * (h / 12))
     .attr('width', w / (d3.max(years) - d3.min(years)))
     .attr('height', h / 12)
     .attr('data-month', d => d.month - 1)
     .attr('data-year', d => d.year)
     .attr('data-temp', d => base + d.variance)
     .attr('class', 'cell')
     .style('fill', d => colorScale(d.variance))
     // set up mouseover to modify tooltip div
     .on('mouseover', (d, i) => {
       tooltip.transition()
              .duration(200)
              .style('opacity', 0.9)
       tooltip.html(`
                ${d.year} - ${months[d.month - 1]}
                <br />
                <br />
                ${(base + d.variance).toFixed(2)}°C
                <br />
                ${d.variance.toFixed(2)}°C
              `)
              .attr('data-year', d.year)
              .style('left', (d3.event.pageX) + 20 + 'px')
              .style('top', (d3.event.pageY) + 'px')
     })
     // set up mouseout to modify tooltip div
     .on('mouseout', d => {
       tooltip.transition()
              .duration(200)
              .style('opacity', 0)
     })
  
  // set up x axis
  const xAxis = d3.axisBottom(xScale)
                  .tickFormat(d3.format('d'))
                  .tickSizeOuter(0)
                  .ticks(20)
  
  // set up y axis
  const yAxis = d3.axisLeft(yScale)
                  .tickSizeOuter(0)
  
  // add axes to chart
  svg.append('g')
     .attr('id', 'x-axis')
     .attr('transform', `translate(0, ${h})`)
     .call(xAxis)  
  svg.append('g')
     .attr('id', 'y-axis')
     .attr('transform', `translate(${margin.left}, 0)`)
     .call(yAxis)
  
  // set up legend
  const legend = svg.append('g')
                    .attr('id', 'legend')
                    .attr('class', 'legend')
                    .attr('transform', `translate(${margin.left}, ${h + 40})`)
  
  // add legend squares
  const sqWidth = 50
  const sqHeight = 50
  
  legend.selectAll('rect')
        .data(colors)
        .enter()
        .append('rect')
        .attr('width', sqWidth)
        .attr('height', sqHeight)
        .attr('x', (d, i) => i * sqWidth)
        .attr('y', 0)
        .style('fill', (d, i) => colors[i])
  
  legend.select('.legend')
        .data()
  
  // set up legend scale
  const legendScale = d3.scaleLinear()
                       .domain(d3.extent(temps))
                       .range([0, colors.length * sqWidth])
  
  let tempTicks = []
  const minTemp = d3.min(temps)
  const maxTemp = d3.max(temps)
  for (let i = 0; i <= 12; i++) {
    if (i === 0) {
      tempTicks.push(minTemp)
    } else if (i > 0 && i < 11) {
      tempTicks.push(tempTicks[i - 1] + ((maxTemp - minTemp) / 11))
    } else if (i === 11) {
      tempTicks.push(maxTemp)
    }
  }
  
  // set up legend axis
  const legendAxis = d3.axisBottom(legendScale)
                       .tickSize(10, 0)
                       .tickFormat(d3.format('.1f'))
                       .tickSizeOuter(0)
                       .tickValues(tempTicks)
  
  legend.append('g')
        .attr('transform', `translate(0, ${sqHeight})`)
        .call(legendAxis)
})
            
          
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