Solving d3.scale is undefined

When porting older code and examples of d3.js visualizations you might encounter the following exception:

TypeError: d3.scale is undefined

The causing code might be something like:

var xscale = d3.scale.linear().range([0, chartWidth]);

The problem is an API change from d3.scale.linear() to d3.scaleLinear() with d3.js 4.0. So to fix it rewrite the code with

var xscale = d3.scaleLinear().range([0, chartWidth]);