index.js

var Starplot = require('./starplot.js')

var plot = new Starplot()
plot.draw(foo)

starplot.js

var d3 = require('d3')

function Starplot() {
  this.data = []
  this.svgContainer = null
}

Starplot.prototype.draw = function(e) {
  this.svgContainer = d3.select(e).append('div')
    .attr('class', 'plot')
    .append('svg')
    .attr('viewBox', '-50 -55 100 100')
}

module.exports = Starplot