(#4861) - faster json parse

src/deps/safeJsonParse.js

diff --git a/src/deps/safeJsonParse.js b/src/deps/safeJsonParse.js
index ee0de96..5100ab2 100644
--- a/src/deps/safeJsonParse.js
+++ b/src/deps/safeJsonParse.js
@@ -1,6 +1,6 @@
 import vuvuzela from 'vuvuzela';
 
-function safeJsonParse(str) {
+function slowJsonParse(str) {
   try {
     return JSON.parse(str);
   } catch (e) {
@@ -9,4 +9,20 @@
   }
 }
 
+function safeJsonParse(str) {
+  // try/catch is deoptimized in V8, leading to slower
+  // times than we'd like to have. Most documents are _not_
+  // huge, and do not require a slower code path just to parse them.
+  // We can be pretty sure that a document under 50000 characters
+  // will not be so deeply nested as to throw a stack overflow error
+  // (depends on the engine and available memory, though, so this is
+  // just a hunch). 50000 was chosen based on the average length
+  // of this string in our test suite, to try to find a number that covers
+  // most of our test cases (26 over this size, 26378 under it).
+  if (str.length < 50000) {
+    return JSON.parse(str);
+  }
+  return slowJsonParse(str);
+}
+
 export default safeJsonParse;
\ No newline at end of file