d3.touches(container[, touches])
Returns the x and y coordinates of the touches associated with the current event relative to the specified container. The container may be an HTML or SVG container element, such as a G element or an SVG element. The coordinates are returned as an array of two-element arrays of numbers [[x1, y1], [x2, y2], …]. If touches is not specified, it defaults to the current event’s touches property.