RunKit + npm: d3-shape

var d3Shape = require("d3-shape"); data = [[0,0], [1,1]]; line = d3Shape.line(data); // make a line console.log(line(data)); // output line curve = d3Shape.curveBasis(); // make a curve line.curve(curve); // set the curve console.log(line.curve()); // check console.log(line(data)); // curve is not function ?