feat: Improve Collision performance

package.json

@@ -1,6 +1,6 @@
 {
   "name": "proton-engine",
-  "version": "5.4.1",
+  "version": "5.4.3",
   "description": "Proton is a simple and powerful javascript particle animation engine.",
   "keywords": [
     "particle",

src/behaviour/Collision.js

@@ -29,8 +29,9 @@ export default class Collision extends Behaviour {
    */
   constructor(emitter, mass, callback, life, easing) {
     super(life, easing);
-
     this.reset(emitter, mass, callback);
+    this.newPool = [];
+    this.pool = [];
     this.name = "Collision";
   }
 
@@ -72,9 +73,13 @@ export default class Collision extends Behaviour {
    * @param {Int} 			index the particle index
    */
   applyBehaviour(particle, time, index) {
-    const newPool = this.emitter ? this.emitter.particles.slice(index) : this.pool.slice(index);
-    const length = newPool.length;
+    if (this.emitter) {
+      Util.sliceArray(this.emitter.particles, index, this.newPool);
+    } else {
+      Util.sliceArray(this.pool, index, this.newPool);
+    }
 
+    const length = this.newPool.length;
     let otherParticle;
     let lengthSq;
     let overlap;
@@ -83,7 +88,7 @@ export default class Collision extends Behaviour {
     let i;
 
     for (i = 0; i < length; i++) {
-      otherParticle = newPool[i];
+      otherParticle = this.newPool[i];
 
       if (otherParticle !== particle) {
         this.delta.copy(otherParticle.p);

src/utils/Util.js

@@ -45,6 +45,13 @@ export default {
     return this.isArray(arr) ? arr : [arr];
   },
 
+  sliceArray(arr1, index, arr2) {
+    this.emptyArray(arr2);
+    for (let i = index; i < arr1.length; i++) {
+      arr2.push(arr1[i]);
+    }
+  },
+
   getRandFromArray(arr) {
     if (!arr) return null;
     return arr[Math.floor(arr.length * Math.random())];