diff --git a/packages/babylon/src/tokenizer/index.js b/packages/babylon/src/tokenizer/index.js
index 444a3448c2..863fef0ef6 100644
--- a/packages/babylon/src/tokenizer/index.js
+++ b/packages/babylon/src/tokenizer/index.js
@@ -28,26 +28,26 @@ import State from "./state";
 const forbiddenNumericSeparatorSiblings = {
   decBinOct: [
     charCodes.dot,
-    charCodes.letterUpperB,
-    charCodes.letterUpperE,
-    charCodes.letterUpperO,
+    charCodes.uppercaseB,
+    charCodes.uppercaseE,
+    charCodes.uppercaseO,
     charCodes.underscore, // multiple separators are not allowed
-    charCodes.letterLowerB,
-    charCodes.letterLowerE,
-    charCodes.letterLowerO,
+    charCodes.lowercaseB,
+    charCodes.lowercaseE,
+    charCodes.lowercaseO,
   ],
   hex: [
     charCodes.dot,
-    charCodes.letterUpperX,
+    charCodes.uppercaseX,
     charCodes.underscore, // multiple separators are not allowed
-    charCodes.letterLowerX,
+    charCodes.lowercaseX,
   ],
 };
 
 const allowedNumericSeparatorSiblings = {};
 allowedNumericSeparatorSiblings.bin = [
   // 0 - 1
-  48,
+  charCodes.digit0,
   49,
 ];
 allowedNumericSeparatorSiblings.oct = [
@@ -64,7 +64,7 @@ allowedNumericSeparatorSiblings.dec = [
   // 0 - 9
   ...allowedNumericSeparatorSiblings.oct,
   56,
-  57,
+  charCodes.digit9,
 ];
 
 allowedNumericSeparatorSiblings.hex = [
@@ -72,17 +72,17 @@ allowedNumericSeparatorSiblings.hex = [
   ...allowedNumericSeparatorSiblings.dec,
   // A - F
   65,
-  charCodes.letterUpperB,
+  charCodes.uppercaseB,
   67,
   68,
-  charCodes.letterUpperE,
+  charCodes.uppercaseE,
   70,
   // a - f
   97,
-  charCodes.letterLowerB,
+  charCodes.lowercaseB,
   99,
   100,
-  charCodes.letterLowerE,
+  charCodes.lowercaseE,
   102,
 ];
 
@@ -401,7 +401,7 @@ export default class Tokenizer extends LocationParser {
   //
   readToken_dot(): void {
     const next = this.input.charCodeAt(this.state.pos + 1);
-    if (next >= 48 && next <= 57) {
+    if (next >= charCodes.digit0 && next <= charCodes.digit9) {
       this.readNumber(true);
       return;
     }
@@ -589,7 +589,10 @@ export default class Tokenizer extends LocationParser {
     if (next === charCodes.questionMark) {
       // '??'
       this.finishOp(tt.nullishCoalescing, 2);
-    } else if (next === charCodes.dot && !(next2 >= 48 && next2 <= 57)) {
+    } else if (
+      next === charCodes.dot &&
+      !(next2 >= charCodes.digit0 && next2 <= charCodes.digit9)
+    ) {
       // '.' not followed by a number
       this.state.pos += 2;
       this.finishToken(tt.questionDot);
@@ -692,30 +695,21 @@ export default class Tokenizer extends LocationParser {
         this.finishToken(tt.backQuote);
         return;
 
-      case 48: {
+      case charCodes.digit0: {
         // '0'
         const next = this.input.charCodeAt(this.state.pos + 1);
         // '0x', '0X' - hex number
-        if (
-          next === charCodes.letterLowerX ||
-          next === charCodes.letterUpperX
-        ) {
+        if (next === charCodes.lowercaseX || next === charCodes.uppercaseX) {
           this.readRadixNumber(16);
           return;
         }
         // '0o', '0O' - octal number
-        if (
-          next === charCodes.letterLowerO ||
-          next === charCodes.letterUpperO
-        ) {
+        if (next === charCodes.lowercaseO || next === charCodes.uppercaseO) {
           this.readRadixNumber(8);
           return;
         }
         // '0b', '0B' - binary number
-        if (
-          next === charCodes.letterLowerB ||
-          next === charCodes.letterUpperB
-        ) {
+        if (next === charCodes.lowercaseB || next === charCodes.uppercaseB) {
           this.readRadixNumber(2);
           return;
         }
@@ -730,7 +724,7 @@ export default class Tokenizer extends LocationParser {
       case 54:
       case 55:
       case 56:
-      case 57: // 1-9
+      case charCodes.digit9: // 1-9
         this.readNumber(false);
         return;
 
@@ -888,7 +882,7 @@ export default class Tokenizer extends LocationParser {
       } else if (code >= 65) {
         val = code - 65 + 10; // A
       } else if (charCodes.isDigit(code)) {
-        val = code - 48; // 0-9
+        val = code - charCodes.digit0; // 0-9
       } else {
         val = Infinity;
       }
@@ -1128,7 +1122,7 @@ export default class Tokenizer extends LocationParser {
         return "\n"; // 'n' -> '\n'
       case 114:
         return "\r"; // 'r' -> '\r'
-      case charCodes.letterLowerX: {
+      case charCodes.lowercaseX: {
         const code = this.readHexChar(2, throwOnInvalid);
         return code === null ? null : String.fromCharCode(code);
       }
@@ -1139,7 +1133,7 @@ export default class Tokenizer extends LocationParser {
       }
       case 116:
         return "\t"; // 't' -> '\t'
-      case charCodes.letterLowerB:
+      case charCodes.lowercaseB:
         return "\b"; // 'b' -> '\b'
       case 118:
         return "\u000b"; // 'v' -> '\u000b'
@@ -1152,7 +1146,7 @@ export default class Tokenizer extends LocationParser {
         ++this.state.curLine;
         return "";
       default:
-        if (ch >= 48 && ch <= 55) {
+        if (ch >= charCodes.digit0 && ch <= 55) {
           const codePos = this.state.pos - 1;
           // $FlowFixMe
           let octalStr = this.input
diff --git a/packages/babylon/src/util/charCodes.js b/packages/babylon/src/util/charCodes.js
index 8ea99ea1c2..3d2b99bb5c 100644
--- a/packages/babylon/src/util/charCodes.js
+++ b/packages/babylon/src/util/charCodes.js
@@ -14,30 +14,97 @@ export const paragraphSeparator = 8233;
 export const asterisk = 42; // '*'
 export const dot = 46; // '.'
 export const slash = 47; // '/'
-export const underscore = 95; // '_'
-
-export const letterUpperB = 66; // 'B'
-export const letterUpperE = 69; // 'E'
-export const letterUpperO = 79; // 'O'
-export const letterUpperX = 88; // 'X'
-
-export const letterLowerN = 110; // 'n'
-export const letterLowerB = 98; // 'b'
-export const letterLowerE = 101; // 'e'
-export const letterLowerO = 111; // 'o'
-export const letterLowerX = 120; // 'x'
-
+export const dash = 45; // '-'
+export const exclamationMark = 33; // '!'
+export const quotationMark = 34; // '"'
+export const numberSign = 35; // '#'
+export const dollarSign = 36; // '$'
+export const percentSign = 37; // '%'
+export const ampersand = 38; // '&'
+export const apostrophe = 39; // '''
+export const leftParenthesis = 40; // '('
+export const rightParenthesis = 41; // ')'
+export const plusSign = 43; // '+'
+export const comma = 44; // ','
 export const digit0 = 48; // '0'
+export const digit1 = 49; // '1'
+export const digit2 = 50; // '2'
+export const digit3 = 51; // '3'
+export const digit4 = 52; // '4'
+export const digit5 = 53; // '5'
+export const digit6 = 54; // '6'
+export const digit7 = 55; // '7'
+export const digit8 = 56; // '8'
 export const digit9 = 57; // '9'
-
+export const colon = 58; // ':'
+export const semicolon = 59; // ';'
 export const lessThan = 60; // '<'
 export const equalsTo = 61; // '='
 export const greaterThan = 62; // '>'
 export const questionMark = 63; // '?'
-export const at = 64; // '@'
-
-export const exclamationMark = 33; // '!'
-export const dash = 45; // '-'
+export const atSign = 64; // '@'
+export const uppercaseA = 65; // 'A'
+export const uppercaseB = 66; // 'B'
+export const uppercaseC = 67; // 'C'
+export const uppercaseD = 68; // 'D'
+export const uppercaseE = 69; // 'E'
+export const uppercaseF = 70; // 'F'
+export const uppercaseG = 71; // 'G'
+export const uppercaseH = 72; // 'H'
+export const uppercaseI = 73; // 'I'
+export const uppercaseJ = 74; // 'J'
+export const uppercaseK = 75; // 'K'
+export const uppercaseL = 76; // 'L'
+export const uppercaseM = 77; // 'M'
+export const uppercaseN = 78; // 'N'
+export const uppercaseO = 79; // 'O'
+export const uppercaseP = 80; // 'P'
+export const uppercaseQ = 81; // 'Q'
+export const uppercaseR = 82; // 'R'
+export const uppercaseS = 83; // 'S'
+export const uppercaseT = 84; // 'T'
+export const uppercaseU = 85; // 'U'
+export const uppercaseV = 86; // 'V'
+export const uppercaseW = 87; // 'W'
+export const uppercaseX = 88; // 'X'
+export const uppercaseY = 89; // 'Y'
+export const uppercaseZ = 90; // 'Z'
+export const leftSquareBracket = 91; // '['
+export const backslash = 92; // '\ '
+export const rightSquareBracket = 93; // ']'
+export const caret = 94; // '^'
+export const underscore = 95; // '_'
+export const graveAccent = 96; // '`'
+export const lowercaseA = 97; // 'a'
+export const lowercaseB = 98; // 'b'
+export const lowercaseC = 99; // 'c'
+export const lowercaseD = 100; // 'd'
+export const lowercaseE = 101; // 'e'
+export const lowercaseF = 102; // 'f'
+export const lowercaseG = 103; // 'g'
+export const lowercaseH = 104; // 'h'
+export const lowercaseI = 105; // 'i'
+export const lowercaseJ = 106; // 'j'
+export const lowercaseK = 107; // 'k'
+export const lowercaseL = 108; // 'l'
+export const lowercaseM = 109; // 'm'
+export const lowercaseN = 110; // 'n'
+export const lowercaseO = 111; // 'o'
+export const lowercaseP = 112; // 'p'
+export const lowercaseQ = 113; // 'q'
+export const lowercaseR = 114; // 'r'
+export const lowercaseS = 115; // 's'
+export const lowercaseT = 116; // 't'
+export const lowercaseU = 117; // 'u'
+export const lowercaseV = 118; // 'v'
+export const lowercaseW = 119; // 'w'
+export const lowercaseX = 120; // 'x'
+export const lowercaseY = 121; // 'y'
+export const lowercaseZ = 122; // 'z'
+export const leftCurlyBrace = 123; // '{'
+export const verticalBar = 124; // '|'
+export const rightCurlyBrace = 125; // '}'
+export const tilde = 126; // '~'
 
 export function isDigit(code: Char): boolean {
   return code >= digit0 && code <= digit9;