const/lettify and fix up

Author: mattgodbolt

eslint.config.js

@@ -4,11 +4,15 @@ import eslintConfigPrettier from "eslint-config-prettier";
 
 /** @type {import('eslint').Linter.Config[]} */
 export default [
+  pluginJs.configs.recommended,
   {
     languageOptions: {
       globals: { ...globals.browser, webkitAudioContext: "readonly" },
     },
+    rules: {
+      "no-var": ["error"],
+      "prefer-const": ["error"],
+    },
   },
-  pluginJs.configs.recommended,
   eslintConfigPrettier,
 ];

src/debug.js

@@ -17,8 +17,8 @@ import { disassemble } from "./z80/z80_dis";
 import { vdp_regs } from "./vdp";
 import { setEventNextEvent, setTstates } from "./z80/z80_ops_full";
 
-var debugSerial = 0;
-var annotations = null;
+let debugSerial = 0;
+let annotations = null;
 
 export function debug_init(romName) {
   debugSerial = (romBanks[1][0x3ffc] << 8) | romBanks[1][0x3ffd];
@@ -50,7 +50,7 @@ export function debug_init(romName) {
 // }
 
 function addressName(addr) {
-  var virtual = virtualAddress(addr);
+  const virtual = virtualAddress(addr);
   if (annotations.labels[virtual]) {
     return (
       '<span class="addr label" title="' +
@@ -64,7 +64,7 @@ function addressName(addr) {
 }
 
 export function addressHtml(addr) {
-  var name = addressName(addr);
+  const name = addressName(addr);
   if (name) {
     return name + " (0x" + hexword(addr) + ")";
   } else {
@@ -73,7 +73,7 @@ export function addressHtml(addr) {
 }
 
 function labelHtml(addr) {
-  var name = addressName(addr);
+  const name = addressName(addr);
   if (name) {
     return name + ":";
   } else {
@@ -88,15 +88,15 @@ function labelHtml(addr) {
 //   setLabel(virtual, content.current);
 // }
 
-var disassPc = 0;
+let disassPc = 0;
 
 function updateDisassembly(address) {
-  var disass = $("#disassembly");
+  const disass = $("#disassembly");
   disassPc = address;
   disass.children().each(function () {
-    var result = disassemble(address);
-    var hex = "";
-    for (var i = address; i < result[1]; ++i) {
+    const result = disassemble(address);
+    let hex = "";
+    for (let i = address; i < result[1]; ++i) {
       if (hex !== "") hex += " ";
       hex += hexbyte(readbyte(i));
     }
@@ -116,13 +116,13 @@ function updateDisassembly(address) {
 
 function prevInstruction(address) {
   for (
-    var startingPoint = address - 20;
+    let startingPoint = address - 20;
     startingPoint !== address;
     startingPoint++
   ) {
-    var addr = startingPoint & 0xffff;
+    let addr = startingPoint & 0xffff;
     while (addr < address) {
-      var result = disassemble(addr);
+      const result = disassemble(addr);
       if (result[1] === address) {
         return addr;
       }
@@ -141,10 +141,10 @@ function updateElement(elem, newVal) {
 }
 
 function updateFlags(f) {
-  var string = "cnp_h_zs";
-  for (var i = 0; i < 8; ++i) {
-    var r = string[i];
-    var elem = $("#z80_flag_" + r);
+  const string = "cnp_h_zs";
+  for (let i = 0; i < 8; ++i) {
+    let r = string[i];
+    const elem = $("#z80_flag_" + r);
     if (f & 1) {
       r = r.toUpperCase();
     }
@@ -157,7 +157,7 @@ function updateFlags(f) {
 
 export function showDebug(pc) {
   $("#debug").show(200);
-  for (var i = 0; i < $("#disassembly").children().length / 2; i++) {
+  for (let i = 0; i < $("#disassembly").children().length / 2; i++) {
     pc = prevInstruction(pc);
   }
   updateDebug(pc);
@@ -168,8 +168,8 @@ function updateDebug(pcOrNone) {
     pcOrNone = disassPc;
   }
   updateDisassembly(pcOrNone);
-  for (var reg in z80) {
-    var elem = $("#z80_" + reg);
+  for (const reg in z80) {
+    const elem = $("#z80_" + reg);
     if (elem) {
       if (
         reg.length > 1 &&
@@ -182,7 +182,7 @@ function updateDebug(pcOrNone) {
       }
     }
   }
-  var i = 0;
+  let i = 0;
   $("#vdp_registers > div:visible .value").each(function () {
     updateElement($(this), hexbyte(vdp_regs[i++]));
   });
@@ -196,7 +196,7 @@ function updateDebug(pcOrNone) {
 export function stepUntil(f) {
   audio_enable(true);
   clearBreakpoint();
-  for (var i = 0; i < 65536; i++) {
+  for (let i = 0; i < 65536; i++) {
     setTstates(0);
     setEventNextEvent(1);
     z80_do_opcodes(cycleCallback);
@@ -207,37 +207,37 @@ export function stepUntil(f) {
 }
 
 export function step() {
-  var curpc = z80.pc;
+  const curpc = z80.pc;
   stepUntil(function () {
     return z80.pc !== curpc;
   });
 }
 
 function isUnconditionalJump(addr) {
-  var result = disassemble(addr);
+  const result = disassemble(addr);
   return !!result[0].match(/^(JR 0x|JP|RET|RST)/);
 }
 
 export function stepOver() {
   if (isUnconditionalJump(z80.pc)) {
     return step();
   }
-  var nextPc = nextInstruction(z80.pc);
+  const nextPc = nextInstruction(z80.pc);
   stepUntil(function () {
     return z80.pc === nextPc;
   });
 }
 
 function isReturn(addr) {
-  var result = disassemble(addr);
+  const result = disassemble(addr);
   return !!result[0].match(/^RET/);
 }
 
 export function stepOut() {
-  var sp = z80.sp;
+  const sp = z80.sp;
   stepUntil(function () {
     if (z80.sp >= sp && isReturn(z80.pc)) {
-      var nextInstr = nextInstruction(z80.pc);
+      const nextInstr = nextInstruction(z80.pc);
       step();
       return z80.pc !== nextInstr;
     }
@@ -249,7 +249,7 @@ export function debugKeyPress(key) {
   if ($("input:visible").length) {
     return true;
   }
-  var keyStr = String.fromCharCode(key);
+  const keyStr = String.fromCharCode(key);
   switch (keyStr) {
     case "k":
       updateDisassembly(prevInstruction(disassPc));

src/main.js

@@ -6,9 +6,9 @@ import { step, stepOver, stepOut } from "./debug";
 
 function loadRomData(name) {
   "use strict";
-  var path = "roms/" + name;
+  const path = "roms/" + name;
   console.log("Loading ROM from " + path);
-  var request = new XMLHttpRequest();
+  const request = new XMLHttpRequest();
   request.open("GET", path, false);
   request.overrideMimeType("text/plain; charset=x-user-defined");
   request.send(null);
@@ -24,7 +24,7 @@ function resetLoadAndStart(filename, romdata) {
 }
 
 function loadUploadFile(file) {
-  var reader = new FileReader();
+  const reader = new FileReader();
   reader.onload = function () {
     resetLoadAndStart(file.name, reader.result);
   };
@@ -45,7 +45,7 @@ function addRomToList(rom) {
 function parseQuery() {
   const parsedQuery = {};
 
-  let queryString =
+  const queryString =
     document.location.search.substring(1) +
     "&" +
     window.location.hash.substring(1);
@@ -63,13 +63,13 @@ function parseQuery() {
 }
 
 function go() {
-  var i;
+  let i;
   hideRomChooser();
   hideAbout();
 
-  var uploadElem = $("#file_upload");
+  const uploadElem = $("#file_upload");
   uploadElem.change(function (e) {
-    var files = e.target.files;
+    const files = e.target.files;
     if (files && files.length) {
       loadUploadFile(files[0]);
     }
@@ -78,11 +78,11 @@ function go() {
   for (i = 0; i < RomList.length; ++i) {
     addRomToList(RomList[i]);
   }
-  var disass = $("#disassembly");
+  const disass = $("#disassembly");
   for (i = 0; i < 32; i++) {
     disass.find(".template").clone().removeClass("template").appendTo(disass);
   }
-  var vdp = $("#vdp_registers");
+  const vdp = $("#vdp_registers");
   for (i = 0; i < 11; i++) {
     vdp
       .find(".template")
@@ -127,7 +127,7 @@ function showRomChooser() {
 }
 
 function clearFileUploadElement() {
-  var uploadElem = $("#file_upload")[0];
+  const uploadElem = $("#file_upload")[0];
   uploadElem.value = "";
 }