Change: serializeString() now only escapes double quote and backslash

Author: rav2040

src/string.ts

@@ -1,70 +1,55 @@
-// A map of strings that can be directly substituted for any code points that need to be escaped.
-const escapeStrings: { [key: number]: string } = {
-  34: '\\"',
-  92: '\\\\',
-};
-
-// Generate UTF-16 hex values for ASCII control characters by converting numbers 0 to 31 to hex values.
-for (let i = 0; i < 32; i++) {
-  escapeStrings[i] = '\\u00' + i.toString(16);
-}
-
-// Generate UTF-16 hex values for surrogate code points by converting numbers 55,296 to 57,343 to hex values.
-for (let i = 55_296; i < 57_344; i++) {
-  escapeStrings[i] = '\\u' + i.toString(16);
-}
+const QUOTATION_MARK = '"';
+const BACKSLASH = '\\';
 
 /**
- * stringifyString() converts a string to a JSON string by escaping any ASCII control characters and lone UTF-16
- * surrogate code points, as well as the double quote and backslash characters, and then returning the resulting string
- * bookended by double quote characters. Control characters and lone surrogate code points are converted to UTF-16 hex
- * values before being escaped. Double quote and backslash characters are simply escaped with a backslash.
+ * Converts a string to a JSON string by escaping any double quote and backslash characters, and then returning the
+ * resulting string bookended by double quotes. ASCII control characters and lone surrogate code points are NOT escaped.
  */
 
-export function stringifyString(value: string): string {
-  let str = '"';
-  let i;
-  let j;
-  let charCode;
-  let nextCharCode;
-
-  for (i = 0, j = 0; i < value.length; i++) {
-    charCode = value.charCodeAt(i);
-
-    if (charCode < 32 || charCode === 34 || charCode === 92) {
-      // The current character is a control character, double quote, or backslash.
-      str += value.slice(j, i) + escapeStrings[charCode];
-      j = i + 1;
-    }
-
-    else if (charCode >= 0xD800 && charCode <= 0xDFFF) {
-      // The current character is a surrogate.
-      if (charCode <= 0xDBFF) {
-        // The current character is a leading surrogate.
-        nextCharCode = value.charCodeAt(i + 1);
+export function serializeString(value: string): string {
+  let result = QUOTATION_MARK;
+  let index;
+  let prevIndex = 0;
 
-        if (nextCharCode >= 0xDC00 && nextCharCode <= 0xDFFF) {
-          // The next character is a trailing surrogate, so skip the next iteration.
-          i++;
-        }
+  let i = value.indexOf(QUOTATION_MARK);
+  let j = value.indexOf(BACKSLASH);
 
-        else {
-          // The current character is a lone leading surrogate.
-          str += value.slice(j, i) + escapeStrings[charCode];
-          j = i + 1;
-        }
+  if (i > -1 && j > -1) {
+    do {
+      if (i < j) {
+        index = i;
+        i = value.indexOf(QUOTATION_MARK, index + 1);
       }
 
       else {
-        // The current character is a lone trailing surrogate.
-        str += value.slice(j, i) + escapeStrings[charCode];
-        j = i + 1;
+        index = j;
+        j = value.indexOf(BACKSLASH, index + 1);
       }
-    }
+
+      result += value.slice(prevIndex, index) + BACKSLASH;
+      prevIndex = index;
+    } while (i > -1 && j > -1)
+  }
+
+  if (i > -1) {
+    do {
+      index = i;
+      i = value.indexOf(QUOTATION_MARK, index + 1);
+
+      result += value.slice(prevIndex, index) + BACKSLASH;
+      prevIndex = index;
+    } while (i > -1)
   }
 
-  // If j is 0 then the string was not altered, so the original string value can be used.
-  str += j === 0 ? value : value.slice(j);
+  else if (j > -1) {
+    do {
+      index = j;
+      j = value.indexOf(BACKSLASH, index + 1);
+
+      result += value.slice(prevIndex, index) + BACKSLASH;
+      prevIndex = index;
+    } while (j > -1)
+  }
 
-  return str + '"';
+  return result + value.slice(prevIndex) + QUOTATION_MARK;
 }