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What is going on in this code?
var a = {a:1};
var b = {b:2};
var c = {};
c[a] = 1;
c[b] === 1 // true!
c[b] = 2;
c[a] === 2 // true!
Specifically, why does using looking up b in c return the value that was stored in a property of a?
What does it mean to use an object as a key to a property in JavaScript?
I've tested this in Chrome/Node and in Firefox.
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Can you use objects as Object keys in JavaScript? # The short answer is "no". All JavaScript object keys are strings.
Methods—setting functions as properties of objects. In JavaScript, you can use functions as values, just like numbers, strings, and objects. That means you can pass them as arguments, return them from other functions, and set them as properties of objects.
Introduction to JavaScript Map object A key of an object must be a string or a symbol, you cannot use an object as a key. An object does not have a property that represents the size of the map.
What does it mean to use an object as a key to a property in JavaScript?
Javascript objects only allow string keys, so your object will first be coerced to a string.
Specifically, why does using looking up b in c return the value that was stored in a property of a?
The string representation of {a: 1} and {b: 2} are both "[object Object]", thus, the property is overwritten.
Edit: If you really need to use objects as keys (I would prefer another solution, if possible), you could use the object's JSON representation:
c[JSON.stringify(a)] = 1
c[JSON.stringify(b)] = 2
But, again, try to think of a different approach. Perhaps the objects have unique identifiers other than the object itself.
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