reduce computation steps

demo/src/script.js

@@ -6,7 +6,7 @@ const height = window.innerHeight
 
 let graph = {
   edges: [],
-  nodes: new Array(128)
+  nodes: new Array(512)
     .fill()
     .map(_ => {
       let direction = Math.random() * 2 * Math.PI

lib/graph-mst.js

@@ -1,39 +1,38 @@
 module.exports = function span(graph) {
-  var prospects = graph.edges.slice()
-  var edges = []
+  var tree = {
+    nodes: graph.nodes.slice(),
+    edges: []
+  }
+  var edges = graph.edges
+    .slice()
+    .sort(function (a, b) { return a.weight - b.weight })
   var indices = [ 0 ]
-  while (prospects.length && indices.length < graph.nodes.length) {
-    var shortest = null
-    var target = null
-    var index = null
-    for (var i = 0; i < indices.length; i++) {
-      var o = indices[i]
-      for (var j = 0; j < prospects.length; j++) {
-        var edge = prospects[j]
-        var a = edge.endpoints[0]
-        var b = edge.endpoints[1]
+  while (indices.length < graph.nodes.length) {
+    for (var i = 0; i < edges.length; i++) {
+      var edge = edges[i]
+      var a = edge.endpoints[0]
+      var b = edge.endpoints[1]
+      for (var j = 0; j < indices.length; j++) {
+        var o = indices[j]
         var t = -1
         if (a === o) {
           t = b
         } else if (b === o) {
           t = a
         }
-        if (t === -1 || indices.indexOf(t) !== -1) continue
-        if (!shortest || edge.weight < shortest.weight) {
-          shortest = edge
-          target = t
-          index = j
+        if (t !== -1) {
+          break
         }
       }
+      if (t !== -1) {
+        if (indices.indexOf(t) === -1) {
+          indices.push(t)
+          tree.edges.push(edge)
+        }
+        edges.splice(i, 1)
+        break
+      }
     }
-    if (shortest) {
-      edges.push(shortest)
-      indices.push(target)
-      prospects.splice(index, 1)
-    }
-  }
-  return {
-    nodes: graph.nodes.slice(),
-    edges: edges
   }
+  return tree
 }