The JavaScript version of the graph drawing library Eclipse Layout Kernel (ELK).
The Eclipse Layout Kernel (ELK) implements an infrastructure to connect diagram editors or viewers to automatic layout algorithms. This library takes the layout-relevant part of ELK and makes it available to the JavaScript world. ELK's flagship is a layer-based layout algorithm that is particularly suited for node-link diagrams with an inherent direction and ports (explicit attachment points on a node's border). It is based on the ideas originally introduced by Sugiyama et al. An example can be seen in the screenshot below.
Note that elkjs is not a diagramming framework itself - it computes positions for the elements of a diagram.
The Eclipse Layout Kernel (or ELK) is two things: a collection of layout algorithms, and an infrastructure that bridges the gap between layout algorithms and diagram viewers and editors.