perf: improve performance to escape big strings

The time to escape strings that contained characters that needed escaping is now lower than before. Native JSON.stringify() got a lot faster in newer versions and may now be used directly. This has to side effect to also reduce the code size a bit.
BridgeAR · Mar 19, 2023 · dbc5143 · dbc5143
1 parent 5c078f2
commit dbc5143
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## v2.4.3
 
 - Fixed replacer function receiving array keys as number instead of string
+- Improved performance to escape long strings that contain characters that need escaping
 
 ## v2.4.2
 

diff --git a/index.js b/index.js
@@ -21,67 +21,15 @@ module.exports = stringify
 
 // eslint-disable-next-line no-control-regex
 const strEscapeSequencesRegExp = /[\u0000-\u001f\u0022\u005c\ud800-\udfff]|[\ud800-\udbff](?![\udc00-\udfff])|(?:[^\ud800-\udbff]|^)[\udc00-\udfff]/
-const strEscapeSequencesReplacer = new RegExp(strEscapeSequencesRegExp, 'g')
-
-// Escaped special characters. Use empty strings to fill up unused entries.
-const meta = [
-  '\\u0000', '\\u0001', '\\u0002', '\\u0003', '\\u0004',
-  '\\u0005', '\\u0006', '\\u0007', '\\b', '\\t',
-  '\\n', '\\u000b', '\\f', '\\r', '\\u000e',
-  '\\u000f', '\\u0010', '\\u0011', '\\u0012', '\\u0013',
-  '\\u0014', '\\u0015', '\\u0016', '\\u0017', '\\u0018',
-  '\\u0019', '\\u001a', '\\u001b', '\\u001c', '\\u001d',
-  '\\u001e', '\\u001f', '', '', '\\"',
-  '', '', '', '', '', '', '', '', '', '',
-  '', '', '', '', '', '', '', '', '', '',
-  '', '', '', '', '', '', '', '', '', '',
-  '', '', '', '', '', '', '', '', '', '',
-  '', '', '', '', '', '', '', '', '', '',
-  '', '', '', '', '', '', '', '\\\\'
-]
-
-function escapeFn (str) {
-  if (str.length === 2) {
-    const charCode = str.charCodeAt(1)
-    return `${str[0]}\\u${charCode.toString(16)}`
-  }
-  const charCode = str.charCodeAt(0)
-  return meta.length > charCode
-    ? meta[charCode]
-    : `\\u${charCode.toString(16)}`
-}
 
 // Escape C0 control characters, double quotes, the backslash and every code
 // unit with a numeric value in the inclusive range 0xD800 to 0xDFFF.
 function strEscape (str) {
   // Some magic numbers that worked out fine while benchmarking with v8 8.0
   if (str.length < 5000 && !strEscapeSequencesRegExp.test(str)) {
-    return str
-  }
-  if (str.length > 100) {
-    return str.replace(strEscapeSequencesReplacer, escapeFn)
-  }
-  let result = ''
-  let last = 0
-  for (let i = 0; i < str.length; i++) {
-    const point = str.charCodeAt(i)
-    if (point === 34 || point === 92 || point < 32) {
-      result += `${str.slice(last, i)}${meta[point]}`
-      last = i + 1
-    } else if (point >= 0xd800 && point <= 0xdfff) {
-      if (point <= 0xdbff && i + 1 < str.length) {
-        const nextPoint = str.charCodeAt(i + 1)
-        if (nextPoint >= 0xdc00 && nextPoint <= 0xdfff) {
-          i++
-          continue
-        }
-      }
-      result += `${str.slice(last, i)}\\u${point.toString(16)}`
-      last = i + 1
-    }
+    return `"${str}"`
   }
-  result += str.slice(last)
-  return result
+  return JSON.stringify(str)
 }
 
 function insertSort (array) {
@@ -237,7 +185,7 @@ function configure (options) {
 
     switch (typeof value) {
       case 'string':
-        return `"${strEscape(value)}"`
+        return strEscape(value)
       case 'object': {
         if (value === null) {
           return 'null'
@@ -313,7 +261,7 @@ function configure (options) {
           const key = keys[i]
           const tmp = stringifyFnReplacer(key, value, stack, replacer, spacer, indentation)
           if (tmp !== undefined) {
-            res += `${separator}"${strEscape(key)}":${whitespace}${tmp}`
+            res += `${separator}${strEscape(key)}:${whitespace}${tmp}`
             separator = join
           }
         }
@@ -351,7 +299,7 @@ function configure (options) {
 
     switch (typeof value) {
       case 'string':
-        return `"${strEscape(value)}"`
+        return strEscape(value)
       case 'object': {
         if (value === null) {
           return 'null'
@@ -407,7 +355,7 @@ function configure (options) {
         for (const key of replacer) {
           const tmp = stringifyArrayReplacer(key, value[key], stack, replacer, spacer, indentation)
           if (tmp !== undefined) {
-            res += `${separator}"${strEscape(key)}":${whitespace}${tmp}`
+            res += `${separator}${strEscape(key)}:${whitespace}${tmp}`
             separator = join
           }
         }
@@ -436,7 +384,7 @@ function configure (options) {
   function stringifyIndent (key, value, stack, spacer, indentation) {
     switch (typeof value) {
       case 'string':
-        return `"${strEscape(value)}"`
+        return strEscape(value)
       case 'object': {
         if (value === null) {
           return 'null'
@@ -512,7 +460,7 @@ function configure (options) {
           const key = keys[i]
           const tmp = stringifyIndent(key, value[key], stack, spacer, indentation)
           if (tmp !== undefined) {
-            res += `${separator}"${strEscape(key)}": ${tmp}`
+            res += `${separator}${strEscape(key)}: ${tmp}`
             separator = join
           }
         }
@@ -546,7 +494,7 @@ function configure (options) {
   function stringifySimple (key, value, stack) {
     switch (typeof value) {
       case 'string':
-        return `"${strEscape(value)}"`
+        return strEscape(value)
       case 'object': {
         if (value === null) {
           return 'null'
@@ -616,7 +564,7 @@ function configure (options) {
           const key = keys[i]
           const tmp = stringifySimple(key, value[key], stack)
           if (tmp !== undefined) {
-            res += `${separator}"${strEscape(key)}":${tmp}`
+            res += `${separator}${strEscape(key)}:${tmp}`
             separator = ','
           }
         }