D3byEX 5.9: Range Bands with Padding (Adapted to D3.js v4)
<!DOCTYPE html>
<html>
<meta charset=utf-8>
<head>
<meta name="description" content="D3.js v4, .scaleBand, .rangeRound,
.padding, ordinal scale range bands" />
</head>
<body>
<script src="http://d3js.org/d3.v4.js"></script>
<script>
var bands = d3.scaleBand() // v4
.domain([0, 1, 2])
.rangeRound([0, 100])
.padding([0.1]);
console.log(bands.range()); // [0, 100]
console.log(bands.bandwidth()); // 29
console.log(bands.padding()); // 0.1
</script>
</body>
</html>