tree.size()

tree.size([size])

If size is specified, sets this tree layout’s size to the specified two-element array of numbers [width, height] and returns this tree layout. If size is not specified, returns the current layout size, which defaults to [1, 1]. A layout size of null indicates that a node size will be used instead. The coordinates x and y represent an arbitrary coordinate system; for example, to produce a radial layout, a size of [360, radius] corresponds to a breadth of 360° and a depth of radius.