Simple Implementation of a Graph

by Ron Eaglin

HTML

<input type="button" onclick="createGraph();" value="Create Graph" /><br/><br/>
This is set up as a button to create the graph. This will allow you to trace the 
entire creation by adding a debugger statement.
<br/>
<br/> Select two nodes:
<br />From
<select id="from"></select>
To
<select id="to"></select>
<input type="button" onclick="calculate();" value="Calculate" /><br/><br/>
The easiest implementation of a graph traversal would be a simple recursive function. You should
research the traversal options for graphs, select one, and implement it here. This is a challenging
assignment requiring research and an understanding of the code.
<br/>
<img src="http://roneaglin.online/cop3530/wp-content/uploads/2017/11/Graph1.jpg" />
<br/>
<p id="nodes"></p>
<br/>
<p id="edges"></p>
<br/>
<br/><span id="result" />

JavaScript

// This is a basic implementation of a Graph
// It has nodes and edges 
// I am using a stack (array in Javascript) to hold info

var Node = function(_name) {
  this.name = _name;
  this.edges = [];
  return this;
}

var Edge = function(_cost) {
  this.from = null;
  this.to = null;
  this.cost = null;
  return this;
}

var Graph = function() {

  // This is a specific implementation of a graph
  // that uses nodes edges and paths. There are many
  // more ways to implement a graph and you should 
  // research them

  this.nodes = [];  // An array of node
  this.edges = [];  // An array of edges
  this.paths = [];  // We need to keep track of paths.

  this.addNode = function(_name) {
    var node = new Node(_name);
    this.nodes.push(node);
    return node;
  };

  this.addEdge = function(_from, _to, _cost) {
    var edge = new Edge(_cost);
    edge.from = _from;
    edge.to = _to;
    edge.cost = _cost;
    this.edges.push(edge);

    // In this implementation of a graph the nodes also 
    // keep a collection of edges. For many traversal algorithms
    // you will need this and should it the edge collection
    // to your nodes here.

    return edge;
  };

  this.printNodes = function() {
    var s = "All Nodes in Graph <br/>";
    for (var i = 0; i < this.nodes.length; i++) {
      s = s + "Node: " + i + "   Name: " + this.nodes[i].name + "</br>";
    }
    return s;
  }

  this.printEdges = function() {
    var s = "All Edges in Graph <br/>";
    for (var i = 0; i < this.edges.length; i++) {
      s += "Edge: " + i + "   From: " + this.edges[i].from.name + "   To: " + this.edges[i].to.name + "   Cost: " + this.edges[i].cost + "</br>";
    }
    return s;
  }


  // Must implement
  this.calculatePaths = function() {
    return this.paths;
  }

  // Must implement
  this.printPaths = function() {
    return this.paths;
  }
}

var nodeList = document.getElementById("nodes");
var graph = new Graph(); // Global
function createGraph() {

  var a =...