Constraint-Based Layout in the Browser.
cola.js (A.K.A. "WebCoLa") is an open-source JavaScript library for arranging your HTML5 documents and diagrams using constraint-based optimization technique - WebCola 
# See also
Cytoscape.js is an open-source graph theory (a.k.a. network) library written in JavaScript. You can use Cytoscape.js for graph analysis and visualisation - cytoscape.org