Use more for...of loops in the code-base

Note that these cases, which are all in older code, were found using the [`unicorn/no-for-loop`](https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/no-for-loop.md) ESLint plugin rule.
However, note that I've opted not to enable this rule by default since there's still *some* cases where I do think that it makes sense to allow "regular" for-loops.

test/resources/reftest-analyzer.js

@@ -301,8 +301,8 @@ window.onload = function () {
 
     // Bind an event handler to each image link
     const images = document.getElementsByClassName("image");
-    for (let i = 0; i < images.length; i++) {
-      images[i].addEventListener(
+    for (const image of images) {
+      image.addEventListener(
         "click",
         function (e) {
           showImages(e.target.id);
@@ -407,9 +407,9 @@ window.onload = function () {
   function flashPixels(on) {
     const stroke = on ? "#FF0000" : "#CCC";
     const strokeWidth = on ? "2px" : "1px";
-    for (let i = 0; i < gFlashingPixels.length; i++) {
-      gFlashingPixels[i].setAttribute("stroke", stroke);
-      gFlashingPixels[i].setAttribute("stroke-width", strokeWidth);
+    for (const pixel of gFlashingPixels) {
+      pixel.setAttribute("stroke", stroke);
+      pixel.setAttribute("stroke-width", strokeWidth);
     }
   }
 

test/stats/statcmp.js

@@ -30,17 +30,13 @@ function parseOptions() {
 
 function group(stats, groupBy) {
   const vals = [];
-  for (let i = 0; i < stats.length; i++) {
-    const curStat = stats[i];
+  for (const curStat of stats) {
     const keyArr = [];
-    for (let j = 0; j < groupBy.length; j++) {
-      keyArr.push(curStat[groupBy[j]]);
+    for (const entry of groupBy) {
+      keyArr.push(curStat[entry]);
     }
     const key = keyArr.join(",");
-    if (vals[key] === undefined) {
-      vals[key] = [];
-    }
-    vals[key].push(curStat.time);
+    (vals[key] ||= []).push(curStat.time);
   }
   return vals;
 }
@@ -134,8 +130,7 @@ function stat(baseline, current) {
     return s.length;
   });
   rows.push(labels);
-  for (let k = 0; k < keys.length; k++) {
-    const key = keys[k];
+  for (const key of keys) {
     const baselineMean = mean(baselineGroup[key]);
     const currentMean = mean(currentGroup[key]);
     const row = key.split(",");
@@ -172,8 +167,7 @@ function stat(baseline, current) {
   // print output
   console.log("-- Grouped By " + options.groupBy.join(", ") + " --");
   const groupCount = options.groupBy.length;
-  for (let r = 0; r < rows.length; r++) {
-    const row = rows[r];
+  for (const row of rows) {
     for (let i = 0; i < row.length; i++) {
       row[i] = pad(row[i], width[i], i < groupCount ? "right" : "left");
     }

test/unit/function_spec.js

@@ -416,10 +416,10 @@ describe("function", function () {
           "destOffset",
           compiledCode
         );
-        for (let i = 0; i < samples.length; i++) {
-          const out = new Float32Array(samples[i].output.length);
-          fn(samples[i].input, 0, out, 0);
-          expect(Array.prototype.slice.call(out, 0)).toEqual(samples[i].output);
+        for (const { input, output } of samples) {
+          const out = new Float32Array(output.length);
+          fn(input, 0, out, 0);
+          expect(Array.prototype.slice.call(out, 0)).toEqual(output);
         }
       }
     }