Replace a bunch of Array.prototype.forEach() cases with for...of loops instead

Using `for...of` is a modern and generally much nicer pattern, since it gets rid of unnecessary callback-functions. (In a couple of spots, a "regular" `for` loop had to be used.)

src/core/evaluator.js

@@ -1394,9 +1394,9 @@ class PartialEvaluator {
       ) {
         const groupIds = [];
         if (Array.isArray(optionalContentGroups)) {
-          optionalContent.get("OCGs").forEach(ocg => {
+          for (const ocg of optionalContentGroups) {
             groupIds.push(ocg.toString());
-          });
+          }
         } else {
           // Dictionary, just use the obj id.
           groupIds.push(optionalContentGroups.objId);

src/core/function.js

@@ -1337,13 +1337,14 @@ var PostScriptCompiler = (function PostScriptCompilerClosure() {
       }
 
       var result = [];
-      instructions.forEach(function (instruction) {
-        var statementBuilder = new ExpressionBuilderVisitor();
+      for (const instruction of instructions) {
+        const statementBuilder = new ExpressionBuilderVisitor();
         instruction.visit(statementBuilder);
         result.push(statementBuilder.toString());
-      });
-      stack.forEach(function (expr, i) {
-        var statementBuilder = new ExpressionBuilderVisitor();
+      }
+      for (let i = 0, ii = stack.length; i < ii; i++) {
+        const expr = stack[i],
+          statementBuilder = new ExpressionBuilderVisitor();
         expr.visit(statementBuilder);
         var min = range[i * 2],
           max = range[i * 2 + 1];
@@ -1359,7 +1360,7 @@ var PostScriptCompiler = (function PostScriptCompilerClosure() {
         out.unshift("dest[destOffset + ", i, "] = ");
         out.push(";");
         result.push(out.join(""));
-      });
+      }
       return result.join("\n");
     }
   }

src/core/worker.js

@@ -785,10 +785,10 @@ class WorkerMessageHandler {
         cancelXHRs(new AbortException("Worker was terminated."));
       }
 
-      WorkerTasks.forEach(function (task) {
+      for (const task of WorkerTasks) {
         waitOn.push(task.finished);
         task.terminate();
-      });
+      }
 
       return Promise.all(waitOn).then(function () {
         // Notice that even if we destroying handler, resolved response promise

src/core/worker_stream.js

@@ -43,10 +43,9 @@ class PDFWorkerStream {
     if (this._fullRequestReader) {
       this._fullRequestReader.cancel(reason);
     }
-    const readers = this._rangeRequestReaders.slice(0);
-    readers.forEach(function (reader) {
+    for (const reader of this._rangeRequestReaders.slice(0)) {
       reader.cancel(reason);
-    });
+    }
   }
 }