Fixed some bugs with a dummy test file (to be removed and replaced with a mocha test).

dummy.js

+var mos6502 = require("./src/MOS6502.js");
+
+var asm = new mos6502.Assembler();
+var src = "DEFINE TOPNT $44\n";
+src += "CLRMEM:\n";
+src += "LDA #$00        ;Set up zero value\n";
+src += "TAY             ;Initialize index pointer\n";
+src += "CLRM1:\n";
+src += "STA (TOPNT),Y   ;Clear memory location\n";
+src += "INY             ;Advance index pointer\n";
+src += "DEX             ;Decrement counter\n";
+src += "BNE CLRM1       ;Not zero, continue checking\n";
+src += "RTS             ;Return\n"
+
+var res = asm.compile(src);
+console.log(res);

src/MOS6502.js

  * Emulate a basic 6502 (MOS) chip.
  */
 
-var Memory = require('src/memory');
+var Memory = require('./memory.js');
 
 class CPU{
   constructor(){
 function tokenize(l){
   var m = l.match(/([^()]+)|([()])/g);
   var ip = false;
-  t = [];
+  var t = [];
   m.forEach((mi)=>{
     if (mi === "("){
       ip = true;
+    } else if (mi === ")"){
+      ip = false;
     } else {
       if (ip){
         mi.split(/[\s,]+/).forEach((i)=>{
       }
     }
   });
+  return t;
 }
 
 class Assembler{
             let lbl = tA.substr(1);
             if (lbl in this.__varlabels){
               if (this.__varlabels[lbl] < 256)
-                v = vlb[lbl];
+                v = this.__varlabels[lbl];
             }
           }
         }
     var op = [];
     src.split("\n").forEach((line)=>{
       line = line.trim();
+      if (line === ""){return;}
       if (line[0] !== ";"){ // Skip comment lines.
         line = line.split(";")[0].trim(); // Take out any trailing comments.
         var tokens = tokenize(line);
 
-        if (tokens[0] === 'define'){
+        if (tokens[0].toLowerCase() === 'define'){
           // Variable label!!
           this.__StoreVarLabel(tokens[1], tokens[2]);  
         } else if (tokens[0][tokens[0].length - 1] === ':'){
           // Jump labels!
-          this.__StoreJmpLabel(tokens[0].substr(0, tokens[0].length - 1);); 
+          this.__StoreJmpLabel(tokens[0].substr(0, tokens[0].length - 1)); 
         } else if (tokens[0].length === 3){
 
           let StoreSingleOp = (code)=>{
             if (tokens.length === 1){
               op.push(code);
               this.__PC += 1;
-              return true;
+              return false;
             }
-            return false;
+            return true;
           };
 
           let StoreBranchOp = (code) => {
             if (tokens.length === 2){
               let v = Number.NaN;
-              if (token[1][0] === '$'){
+              if (tokens[1][0] === '$'){
                 if (tokens[1].length === 3 || tokens[1].length === 5){
                   v = parseInt(token[1].substr(1), 16);
                 }
                 op.push(code);
                 op.push((v >= 0) ? v : v + 255);
                 this.__PC += 2;
+                return false;
               }
             }
-            return false;
+            return true;
           };
 
           let StoreOp = (codes, mint, maxt) => {
             if (tokens.length >= mint && tokens.length <= maxt){
-              let mv = addrModeVal(tokens[1], (tokens.length === 3) ? tokens[2].toUpperCase(), null);
-              let modea = true;
+              let mv = this.__AddrModeVal(tokens[1], (tokens.length === 3) ? tokens[2].toUpperCase() : null);
+              let modena = true;
               switch(mv[0]){
                 case "i":
-                  modea = codes[0] !== null;
-                  if (modea){
+                  modena = codes[0] === null;
+                  if (!modena){
                     op.push(codes[0]);
                     op.push(mv[1]);
                     this.__PC += 2;
                   } break;
                 case "z":
-                  modea = codes[1] !== null;
-                  if (modea){
+                  modena = codes[1] === null;
+                  if (!modena){
                     op.push(codes[1]);
                     op.push(mv[1]);
                     this.__PC += 2;
                   } break;
                 case "zX":
-                  modea = codes[2] !== null;
-                  if (modea){
+                  modena = codes[2] === null;
+                  if (!modena){
                     op.push(codes[2]);
                     op.push(mv[1]);
                     this.__PC += 2;
                   } break;
                 case "a":
-                  modea = codes[3] !== null;
-                  if (modea){
+                  modena = codes[3] === null;
+                  if (!modena){
                     op.push(codes[3]);
                     op.push(mv[1] & 0x000000FF);
                     op.push((mv[1] & 0x0000FF00) >> 8);
                     this.__PC += 3;
                   } break;
                 case "aX":
-                  modea = codes[4] !== null;
-                  if (modea){
+                  modena = codes[4] === null;
+                  if (!modena){
                     op.push(codes[4]);
                     op.push(mv[1] & 0x000000FF);
                     op.push((mv[1] & 0x0000FF00) >> 8);
                     this.__PC += 3;
                   } break;
                 case "aY":
-                  modea = codes[5] !== null;
-                  if (modea){
+                  modena = codes[5] === null;
+                  if (!modena){
                     op.push(codes[5]);
                     op.push(mv[1] & 0x000000FF);
                     op.push((mv[1] & 0x0000FF00) >> 8);
                     this.__PC += 3;
                   } break;
                 case "nX":
-                  modea = codes[6] !== null;
-                  if (modea){
+                  modena = codes[6] === null;
+                  if (!modena){
                     op.push(codes[6]);
                     op.push(mv[1]);
                     this.__PC += 2;
                   } break;
                 case "nY":
-                  modea = codes[7] !== null;
-                  if (modea){
+                  modena = codes[7] === null;
+                  if (!modena){
                     op.push(codes[7]);
                     op.push(mv[1]);
                     this.__PC += 2;
                   } break;
               }
-              if (modea === false)
+              if (modena)
                 throw new Error("Op-code does not support implied mode on program address " + toHexString(this.__PC));
-              return true;
+              return false;
             }
-            return false;
+            return true;
           };
 
           let procFailed = false;
               break;
 // --- LDA
             case 'lda':
-              procFailed = StoreOp([0xA9, 0xA5, 0xB5, 0xAD, 0xBD, 0xB9, 0xA1, 0xB1], 2, 3); break; 
-              break;
+              procFailed = StoreOp([0xA9, 0xA5, 0xB5, 0xAD, 0xBD, 0xB9, 0xA1, 0xB1], 2, 3); break;
 // --- LDX
             case 'ldx':
               procFailed = StoreOp([0xA2, 0xA6, 0xB6, 0xAE, 0xBE, null, null, null], 2, 3); break;
-              break;
 // --- LDY
             case 'ldy':
               procFailed = StoreOp([0xA0, 0xA4, 0xB4, 0xAC, 0xBC, null, null, null], 2, 3); break;
-              break;
 // --- LSR
             case 'lsr':
               if (tokens.length === 2){