add graph creation conveniences

Author: WardCunningham

src/graph.js

@@ -16,7 +16,13 @@ export class Graph {
     return this.nodes.length-1;
   }
 
+  addUniqNode(type, props={}) {
+    const nid = this.nodes.findIndex(node => node.type == type && node.props?.name == props?.name)
+    return nid >= 0 ? nid : this.addNode(type, props)
+  }
+
   addRel(type, from, to, props={}) {
+    if (from == null || to == null) return null
     const obj = {type, from, to, props};
     this.rels.push(obj);
     const rid = this.rels.length-1;

test/create.test.js

@@ -0,0 +1,29 @@
+'use strict';
+
+// Graph tests for graph creation conveniences
+// usage: deno test  // from parent project's root dir
+
+import {assertEquals } from "https://deno.land/std@0.126.0/testing/asserts.ts";
+import {Graph} from '../src/graph.js';
+
+Deno.test("Adding Unique Nodes Only Once", () => {
+  const g = new Graph();
+  g.addNode('God')
+  g.addNode('Man',{name:'Adam'})
+  g.addNode('Woman',{name:'Eve'})
+  assertEquals(g.size(), 3);
+  g.addUniqNode('Man',{name:'Adam'})
+  g.addUniqNode('God')
+  assertEquals(g.size(), 3);
+});
+
+Deno.test("Ignore Rels for Nodes Null or Undefined", () => {
+  const g = new Graph();
+  let nid = g.addNode('Man',{name:'Adam'})
+  let rid = g.addRel('',nid,nid)
+  assertEquals(rid, 0)
+  rid = g.addRel('',null,nid)
+  assertEquals(rid, null)
+  rid = g.addRel('',nid,undefined)
+  assertEquals(rid, null)
+});