Margin Convention with D3

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    .chart {
      background: lightgray;
      border: 1px solid black;
      width: 425px;
      height: 625px;
    }
  </style>
</head>

<body>
  <div class="chart"></div>
  <script>
    // Feel free to change or delete any of the code you see in this editor!
    var margin = { top: 10, right: 10, bottom: 25, left: 25}
    var width = 425 - margin.left - margin.right
    var height = 625 - margin.top - margin.bottom

var svg = d3.select('.chart')
    			.append('svg')
    			.attr('width', width + margin.left + margin.right)
    			.attr('height', height + margin.top + margin.bottom)
    		.append('g')
    			.attr('transform', `translate(${margin.left}, ${margin.top})`)
   
    svg.append('rect')
    	.attr('width', width/2)
    	.attr('height', height)
    	.style('fill', 'lightblue')
    	.style('stroke', 'lightgreen')
    
    svg.append('rect')
    	.attr('x', width/2)
      .attr('width', width/2)
    	.attr('height', height)
    	.style('fill', 'lightyellow')
    	.style('stroke', 'lightgreen')

</script>
</body>

https://d3js.org/d3.v4.min.js