made code more functional

README.md

@@ -1 +1,5 @@
-# Hack-Assembler
+# Hack Assembler
+This is an assembler from the Hack assembly language into the Hack machine language. [Try for yourself here](https://evoniuk.github.io/Hack-Assembler/).
+
+## The Hack Language
+Hack is a language developed for the conceptual Hack computer, built as a part of [the Nand To Tetris course](https://www.nand2tetris.org). Hack is a 16 bit computer.

main.js

@@ -11,9 +11,8 @@ document.getElementById('inputCode').addEventListener('click', function() {
 
 function displayCode (code) {
   const outputOriginal = document.getElementById('outputOriginal');
-  outputOriginal.textContent = '';
-
   const outputArea = document.getElementById('output');
+  outputOriginal.textContent = '';
   outputArea.textContent = '';
 
   const processedCode = process(code);
@@ -29,8 +28,7 @@ function displayCode (code) {
 }
 
 function process(code) {
-  code = parse(code);
-  code = handleSymbols(code);
-  originalCode = code.map(line => line);
-  return [originalCode, assemble(code)];
+  const parsedCode = parse(code);
+  const unSymbolized = handleSymbols(parsedCode);
+  return [unSymbolized, assemble(unSymbolized)];
 }

src/assemble.js

@@ -1,22 +1,15 @@
 function assemble(code) {
-  for (let i = 0; i < code.length; i++) {
-    if (code[i][0] === '@')
-      code[i] = assembleAinstruction(code[i]);
-    else code[i] = assembleCinstruction(code[i]);
-  }
-
-  return code;
+  return code.map(line => line[0] === '@' ?
+    assembleAinstruction(line):
+    assembleCinstruction(line));
 }
 
 function assembleAinstruction(line) {
-  let num = line.substring(1);
-  num = parseInt(num, 10).toString(2);
-
-  let result = '0';
-  for (let i = 0; i < 15 - num.length; i++)
-    result += '0';
+  const num = line.substring(1);
+  const binaryNum = parseInt(num, 10).toString(2);
+  const leadingZeros = '0'.repeat(16 - binaryNum.length);
 
-  return result + num;
+  return leadingZeros + binaryNum;
 }
 
 function assembleCinstruction(line) {
@@ -30,8 +23,8 @@ function assembleCinstruction(line) {
 
 function parseCinstruction(line) {
   // splits into [dest, comp, jmp]
-  let splitLine = line.split(/[=;]+/);
-  if (!line.includes('=')) splitLine = [''].concat(splitLine);
+  const splitLine = line.split(/[=;]+/);
+  if (!line.includes('=')) splitLine.unshift('')
   if (!line.includes(';')) splitLine.push('');
 
   return splitLine;
@@ -47,37 +40,37 @@ function getDestCode(dest) {
 function getCompCode(comp) {
   const aBit = comp.includes('M') ? '1' : '0';
 
-  comp = comp.replace(/A|M/, 'X');
+  const compare = comp.replace(/A|M/, 'X');
   const cBits =
-    comp === '0'   ? '101010':
-    comp === '1'   ? '111111':
-    comp === '-1'  ? '111010':
-    comp === 'D'   ? '001100':
-    comp === 'X'   ? '110000':
-    comp === '!D'  ? '001101':
-    comp === '!X'  ? '110001':
-    comp === '-D'  ? '001111':
-    comp === '-X'  ? '110011':
-    comp === 'D+1' ? '011111':
-    comp === 'X+1' ? '110111':
-    comp === 'D-1' ? '001110':
-    comp === 'X-1' ? '110010':
-    comp === 'D+X' ? '000010':
-    comp === 'D-X' ? '010011':
-    comp === 'X-D' ? '000111':
-    comp === 'D&X' ? '000000':
-                     '010101';
+    compare === '0'   ? '101010':
+    compare === '1'   ? '111111':
+    compare === '-1'  ? '111010':
+    compare === 'D'   ? '001100':
+    compare === 'X'   ? '110000':
+    compare === '!D'  ? '001101':
+    compare === '!X'  ? '110001':
+    compare === '-D'  ? '001111':
+    compare === '-X'  ? '110011':
+    compare === 'D+1' ? '011111':
+    compare === 'X+1' ? '110111':
+    compare === 'D-1' ? '001110':
+    compare === 'X-1' ? '110010':
+    compare === 'D+X' ? '000010':
+    compare === 'D-X' ? '010011':
+    compare === 'X-D' ? '000111':
+    compare === 'D&X' ? '000000':
+                        '010101';
 
   return aBit + cBits;
 }
 
 function getJumpCode(jump) {
   return jump === '' ? '000':
-    jump === 'JGT' ? '001':
-    jump === 'JEQ' ? '010':
-    jump === 'JGE' ? '011':
-    jump === 'JLT' ? '100':
-    jump === 'JNE' ? '101':
-    jump === 'JLE' ? '110':
-                     '111';
+      jump === 'JGT' ? '001':
+      jump === 'JEQ' ? '010':
+      jump === 'JGE' ? '011':
+      jump === 'JLT' ? '100':
+      jump === 'JNE' ? '101':
+      jump === 'JLE' ? '110':
+                       '111';
 }

src/handleSymbols.js

@@ -25,14 +25,14 @@ function handleSymbols(code) {
     THAT: 4,
   };
 
-  code = handleLabels(code, symbolTable);
-  code = handleVariables(code, symbolTable);
+  enterLabelsIntoSymbolTable(code, symbolTable);
+  enterVarsIntoSymbolTable(code, symbolTable);
 
-  return code;
+  const noLabels = code.filter(line => line[0] !== '(');
+  return replaceVars(noLabels, symbolTable);
 }
 
-function handleLabels(code, symbolTable) {
-  // enter value of labels into symbol table
+function enterLabelsIntoSymbolTable(code, symbolTable) {
   let numberOfLabelsSeen = 0;
   for (let i = 0; i < code.length; i++) {
     if (code[i][0] === '(') {
@@ -41,25 +41,19 @@ function handleLabels(code, symbolTable) {
       numberOfLabelsSeen++;
     }
   }
-
-  // remove labels from code
-  return code.filter(line => line[0] !== '(');
 }
 
-function handleVariables(code, symbolTable) {
-  // enter variables into symbol table
+function enterVarsIntoSymbolTable(code, symbolTable) {
   let variableIndex = 16;
   for (let i = 0; i < code.length; i++)
     if (lineIsNewVariable(code[i], symbolTable))
       symbolTable[code[i].substring(1)] = variableIndex++;
+}
 
-  // enter value of variables and labels where they occur
-  for (let i = 0; i < code.length; i++) {
-    if (code[i][0] === '@' && code[i].substring(1) in symbolTable)
-      code[i] = '@' + symbolTable[code[i].substring(1)];
-  }
-
-  return code;
+function replaceVars(code, symbolTable) {
+  return code.map(line => line[0] === '@' && line.substring(1) in symbolTable ?
+    '@' + symbolTable[line.substring(1)]:
+    line)
 }
 
 function lineIsNewVariable(line, symbolTable) {

src/parser.js

@@ -1,18 +1,11 @@
 function parse(code) {
-  code = code.split(/\r?\n/); // splits each line
-  return code.map(stripWhitespace).filter(line => line !== '');
+  lines = code.split(/\r?\n/); // splits each line
+  return lines.map(stripWhitespace).filter(line => line !== '');
 }
 
 function stripWhitespace(line) {
-  if (line[0] === '/') return ''; // remove line comments
-  line = line.replace(/\s/g,'');  // remove spaces
-
-  // remove inline comments
-  let result = '';
-  for (let i = 0; i < line.length; i++) {
-    if (line[i] === '/') break;
-    result += line[i];
-  }
-
-  return result;
+  noSpaces = line.replace(/\s/g,'');  // remove spaces
+  return noSpaces.includes('/') ?
+    noSpaces.substring(0, noSpaces.indexOf('/')):
+    noSpaces;
 }