mouse x & y

<!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; }
  </style>
</head>

<body>
  <script>
    
    const margin = {top: 20, left: 20, right: 100};
    let svg = d3.select("body").append("svg")
      .attr("width", window.innerWidth)
      .attr("height", window.innerHeight)
    	//.append('g')
    	//.attr('transform', `translate(${margin.left}, ${margin.top})`);
    
    let x = d3.scaleLinear().domain([0, 100]).range([0, window.innerWidth - margin.right]).clamp(true)
    let y = d3.scaleLinear().domain([0, 100]).range([0, window.innerHeight])
    
    svg.append('line')
    	.attr('x1', 0)
    	.attr('y1', 0)
    	.attr('x2', 0)
    	.attr('y2', 0)
    	.classed('line', true)
    	.style('stroke', 'rgb(231, 93, 135)')
    	.style('stroke-width', 5);

svg.on('mousemove', () => {
      
      d3.select('.line')
      	.attr('x2', x(x.invert(d3.event.x)))
    		.attr('y2', y(y.invert(d3.event.y)))
      
      console.log('x event',d3.event.x)
      console.log('x invert',x.invert(d3.event.x))
      console.log('x ()',x(x.invert(d3.event.x)))
      console.log('y',y.invert(d3.event.y))
    });
    
    svg.call(d3.axisTop(x))

</script>
</body>

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