US City temperature visualisation

a simple visualzation for city temprature with Y axis starting at 0 Position.

<!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; }
    svg {
      width: 100%;
      height: 100%;
    }
  </style>
</head>

<body>
  <h3>Temprature visualization for New York </h3>
  <svg></svg>
  <script>
    // change the city below to change between NY, SF and Austin
    var city = 'New York';
    var width = 800;
    var height = 300;
    var margin = {top:20, bottom:20, left:40, right:20};
    
    // dataset for each temprature across day
    d3.tsv('data.tsv', (err, data) => {

// clean the data
      data.forEach(d => {
        d.date = d3.timeParse("%Y%m%d")(d.date);
        d.date = new Date(d.date); //x
        d[city] = ++d[city]; // y
      });
      
      // scales
      var xExtent = d3.extent(data, d => d.date);

var xScale = d3.scaleTime()
      	.domain(xExtent)
      	.range([margin.left, width - margin.right]);
      
      var yExtent = d3.extent(data, d => d[city]);
      var yMax = d3.max(data, d => d[city]) // this is required to start y at 0

var yScale = d3.scaleLinear()
      	.domain([0, yMax]) // this will start at 0 position regardless of data
//       		.domain(yExtent) // this will start at actual minimum value
      	.range([height - margin.bottom, margin.top]);
      
      var heightScale = d3.scaleLinear()
      	.domain([0, yMax]) // this is when you have yaxis starts at 0
//       	.domain(yExtent) // this is when you use yExtent in the scale
      	.range([0, height - margin.top - margin.bottom]);

// create the rectangles
      var svg = d3.select('svg');
      
      var rect = svg.selectAll('rect')
      	.data(data)
      	.enter().append('rect')
      	.attr('width', 2)
      	.attr('height', function(d){
          return heightScale(d[city]);
        })
      	.attr('x', function(d) { return xScale(d.date)})
      	.attr('y', function(d) { return yScale(d[city])})
      	.attr('fill', 'blue')
      	.attr('stroke', 'white');
      
     // create axis
      var xAxis = d3.axisBottom()
      	.scale(xScale)
      	.tickFormat(d => d3.timeFormat('%b %Y')(d));
      var yAxis = d3.axisLeft()
      	.scale(yScale);
      
      svg.append('g')
      	.attr('transform', 'translate(' + [0, height - margin.bottom] + 
             ')')
      	.call(xAxis)
      svg.append('g')
      	.attr('transform', 'translate(' +[margin.left, 0] + ')')
      	.call(yAxis);
      
    })
  </script>
</body>

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