If you're running Node 0.12+ or io.js,
deeperwill use the built-in
Buffer.equals(). If you're running an older version of Node and you install Ben Noordhuis's buffertools into a project using
deeper, it will use that to speed up comparison of Buffers. This used to be installed as an optional dependency, but it gets in the way of browserification and also makes using
deeperin your own projects harder, so I changed it to just try to use it if it's there.
It has some optimizations, but stresses correctness over raw speed (unless you're testing objects with lots of Buffers attached to them, in which case it plus
buffertoolsis likely to be the fastest general-purpose deep-comparison tool available).
The core algorithm is based on those used by Node's assertion library and the implementation of cycle detection in isEqual in Underscore.js.
I like to think the documentation is pretty OK.
npm install deeper
// vanilla var deepEqual = require('deeper') if (!deepEqual(obj1, obj2)) console.log("yay! diversity!");
detailsCopied from the source, here are the details of
===only tests objects and functions by reference.
nullis an object.
Any pairs of identical entities failing this test are therefore objects (including `null`), which need to be recursed into and compared attribute by attribute.
- Since the only entities to get to this test must be objects, if
is not an object, they're clearly not the same. All unfiltered `a` and `b` getting past this are objects (including `null`).
nullis an object, but
null === null.All unfiltered
- Buffers need to be special-cased because they live partially on the wrong
- It's much faster to compare dates by numeric value (
.getTime()) than by
RegExpsby their components, not the objects themselves.
- Treat argumens objects like arrays. The parts of an arguments list most
people care about are the arguments themselves, not `callee`, which you shouldn't be looking at anyway.
- Objects are more complex:
1. Ensure that `a` and `b` are on the same constructor chain. 2. Ensure that `a` and `b` have the same number of own properties (which is what `Object.keys()` returns). 3. Ensure that cyclical references don't blow up the stack. 4. Ensure that all the key names match (faster). 5. Ensure that all of the associated values match, recursively (slower).
(somewhat untested) assumptions:
- Functions are only considered identical if they unify to the same reference.
- V8 is smart enough to optimize treating an Array like any other kind of
- Users of this function are cool with mutually recursive data structures that