d3-force-elastic/dist/d3-force-elastic.js

A Hooke's law spring-like attraction force between node pairs for the d3-force simulation engine.

// Version 1.0.0 d3-force-elastic - https://github.com/vasturiano/d3-force-elastic
(function (global, factory) {
  typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) :
  typeof define === 'function' && define.amd ? define(['exports'], factory) :
  (global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.d3 = global.d3 || {}));
})(this, (function (exports) { 'use strict';

  function _typeof(o) {
    "@babel/helpers - typeof";

    return _typeof = "function" == typeof Symbol && "symbol" == typeof Symbol.iterator ? function (o) {
      return typeof o;
    } : function (o) {
      return o && "function" == typeof Symbol && o.constructor === Symbol && o !== Symbol.prototype ? "symbol" : typeof o;
    }, _typeof(o);
  }

  function constant (x) {
    return function () {
      return x;
    };
  }

  function elastic () {
    var links = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : [];
    var nDim,
      nodes = [],
      id = function id(node) {
        return node.index;
      },
      // accessor: node unique id
      distance = function distance(link) {
        return 30;
      },
      // accessor: number
      elasticity = function elasticity(link) {
        return 0.8;
      }; // accessor: number between 0 and 1

    function force(alpha) {
      for (var i = 0; i < links.length; i++) {
        var link = links[i],
          dx = link.target.x - link.source.x,
          dy = link.target.y - link.source.y || 0,
          dz = link.target.z - link.source.z || 0,
          d = calcDist(dx, dy, dz);
        var linkLen = distance(link);
        if (d <= linkLen) continue; // Elastic not extended, no effect

        var strength = alpha * elasticity(link) * (d - linkLen);

        // Move only one side if opposite node is fixed
        var bias = link.source.fx != null ? 0 : link.target.fx != null ? 1 : 0.5;
        var srcAcceleration = strength * bias;
        var tgtAcceleration = strength * (1 - bias);
        link.source.vx += dx / d * srcAcceleration;
        link.target.vx -= dx / d * tgtAcceleration;
        if (nDim > 1) {
          link.source.vy += dy / d * srcAcceleration;
          link.target.vy -= dy / d * tgtAcceleration;
        }
        if (nDim > 2) {
          link.source.vz += dz / d * srcAcceleration;
          link.target.vz -= dz / d * tgtAcceleration;
        }
      }
    }
    function initialize() {
      var nodesById = new Map(nodes.map(function (d, i) {
        return [id(d, i, nodes), d];
      }));
      links.forEach(function (link) {
        if (_typeof(link.source) !== "object") link.source = nodesById.get(link.source) || link.source;
        if (_typeof(link.target) !== "object") link.target = nodesById.get(link.target) || link.target;
      });
    }
    force.initialize = function (initNodes) {
      nodes = initNodes;
      for (var _len = arguments.length, args = new Array(_len > 1 ? _len - 1 : 0), _key = 1; _key < _len; _key++) {
        args[_key - 1] = arguments[_key];
      }
      nDim = args.find(function (arg) {
        return [1, 2, 3].includes(arg);
      }) || 2;
      initialize();
    };
    force.links = function (_) {
      return arguments.length ? (links = _, initialize(), force) : links;
    };
    force.id = function (_) {
      return arguments.length ? (id = _, force) : id;
    };
    force.distance = function (_) {
      return arguments.length ? (distance = typeof _ === 'function' ? _ : constant(+_), force) : distance;
    };
    force.elasticity = function (_) {
      return arguments.length ? (elasticity = typeof _ === 'function' ? _ : constant(+_), force) : elasticity;
    };
    return force;
  }

  //

  function calcDist(x) {
    var y = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 0;
    var z = arguments.length > 2 && arguments[2] !== undefined ? arguments[2] : 0;
    return Math.sqrt(x * x + y * y + z * z);
  }

  exports.forceElastic = elastic;

}));
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