fix: Incremental lexing (#132)

* refactor: Tokenizer Class

* Update test

fixtures/asts-with-range/string-10-single-quote-escapes-json5.txt

@@ -51,12 +51,12 @@
             },
             "range": [
                 0,
-                74
+                75
             ]
         }
     ],
     "range": [
         0,
         75
     ]
-}
+}

js/src/char-code-reader.js

@@ -151,6 +151,20 @@ export class CharCodeReader {
         return this.#text.charCodeAt(this.#offset + 1);
     }
 
+    /**
+     * Determines if the next character code in the text matches a specific character code.
+     * @param {(number) => boolean} fn A function to call on the next character.
+     * @returns {boolean} True if the next character code matches, false if not.
+     */ 
+    match(fn) {
+        if (fn(this.peek())) {
+            this.next();
+            return true;
+        }
+
+        return false;
+    }
+
     /**
      * Returns the last character code read.
      * @returns {number} The last character code read.

js/src/errors.js

@@ -63,6 +63,21 @@ export class UnexpectedChar extends ErrorWithLocation {
     }
 }
 
+/**
+ * Error thrown when an unexpected identifier is found during tokenizing.
+ */
+export class UnexpectedIdentifier extends ErrorWithLocation {
+
+    /**
+     * Creates a new instance.
+     * @param {string} unexpected The character that was found.
+     * @param {Location} loc The location information for the found character.
+     */
+    constructor(unexpected, loc) {
+        super(`Unexpected identifier '${ unexpected }' found.`, loc);
+    }
+}
+
 /**
  * Error thrown when an unexpected token is found during parsing.
  */