From 2dbb470ea10697f7514094934dfbf635969b8566 Mon Sep 17 00:00:00 2001 From: Nathan Rajlich Date: Tue, 25 Oct 2011 21:42:23 -0700 Subject: [PATCH] Don't use `instanceof` in lib/util.js "is" checks. While using `instanceof`, these functions could easily be faked with something like: Object.create(Date.prototype) So let's just not use it at all. A little slower, but these functions are only used in the REPL / for debugging so it's OK. Fixes #1941. Fixes #1942. --- lib/util.js | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/lib/util.js b/lib/util.js index 098aab2..07e2e3b 100644 --- a/lib/util.js +++ b/lib/util.js @@ -378,31 +378,29 @@ function reduceToSingleString(output, base, braces) { } +// NOTE: These type checking functions intentionally don't use `instanceof` +// because it is fragile and can be easily faked with `Object.create()`. function isArray(ar) { - return ar instanceof Array || - Array.isArray(ar) || - (ar && ar !== Object.prototype && isArray(ar.__proto__)); + return Array.isArray(ar) || + (typeof ar === 'object' && objectToString(ar) === '[object Array]'); } exports.isArray = isArray; function isRegExp(re) { - return re instanceof RegExp || - (typeof re === 'object' && objectToString(re) === '[object RegExp]'); + return typeof re === 'object' && objectToString(re) === '[object RegExp]'; } exports.isRegExp = isRegExp; function isDate(d) { - return d instanceof Date || - (typeof d === 'object' && objectToString(d) === '[object Date]'); + return typeof d === 'object' && objectToString(d) === '[object Date]'; } exports.isDate = isDate; function isError(e) { - return e instanceof Error || - (typeof e === 'object' && objectToString(e) === '[object Error]'); + return typeof e === 'object' && objectToString(e) === '[object Error]'; } exports.isError = isError; -- 2.7.4