I was reading javascript questions where i found this piece of code
var a={},
b={key:'b'},
c={key:'c'};
a[b] = 123;
a[c] = 456;
console.log(a[b]); // o/p - 456
can anybody make me understand this code why and how it is printing 456 ?
And I think we can use dot ie ab = 123
and string a['b'] = 123
approach to add property to an object.
Both b
and c
resolve to the same string ( [object Object]
). Hence you are overwriting the same key.
And I think we can use dot ie ab = 123 and string a['b'] = 123 approach to add property to an object.
Yes you can, but a['b']
is very different from a[b]
. The first one resolves to a key with a string value just as it shows ( 'b'
), where as the other one will depend on the stringified value of the variable b
(in this case is [object Object]
).
For really using the content of the object, you may use the stringified version.
var a = {}, b = { key: 'b' }, c = { key: 'c' }; a[JSON.stringify(b)] = 123; a[JSON.stringify(c)] = 456; console.log(a[JSON.stringify(b)]);
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