I know the difference between == and === when applied to primitive values. But for objects, they both seem to be a simple identity comparison.
var a = {} var b = a var c = {} a == b // true a === b // true a == c // false a === c // false Is there any situation where comparing two objects will provide different results for each operator, or are they functionally equivalent?
Yes, comparing two objects with == is the same as comparing them with ===. Just as comparing two strings with == is the same as ===. If the type of values are the same, both comparing methods will give the same result. As the specification states:
7.2.14 Abstract Equality Comparison
The comparison x == y, where x and y are values, produces true or false. Such a comparison is performed as follows:
- If Type(x) is the same as Type(y), then
- Return the result of performing Strict Equality Comparison x === y.
Looks like it
The only way I know to "check for object equality" in javascript is to deep check every possible key (but even then it is just duck type checking)
The extra = in === ensures both sides are of the same type. a and c both are objects, the same type. So == or === is irrelevant here.
Well... === is "compare identity and type". You've determined that you're comparing two objects (so "type" is the same), that leaves "compare identity", which is the same as ==.
Likewise, if you compare two numbers, since you already know they are the same type (number), === is the same as ==. There is nothing special or different about objects vs. primitives here. It's just that the only type for objects is object.
