Set search time slower than object?

Question

Out of curiosity, I decided to confirm my belief that the implementation of Set is faster than Object (works in google chrome) in terms of insertion / addition and search. My results were a bit confusing.

x = {};
y = new Set();

console.time('Insert into Object');
for (var i = 0; i < 1000000; i++) {
    x[i] = 0;
}
console.timeEnd('Insert into Object');

console.time('Insert into Set');
for (i = 0; i < 1000000; i++) {
    y.add(i);
}
console.timeEnd('Insert into Set');

var t = 0;

console.time('Retrieve from Object');
for (i = 0; i < 1000000; i++) {
    t = x[i];
}
console.timeEnd('Retrieve from Object');

console.time('Retrieve from Set');
for (i = 0; i < 1000000; i++) {
    t = y.has(i);
}
console.timeEnd('Retrieve from Set');

VM19742:9  Insert into Object: 1341.777ms
VM19742:15 Insert into Set: 1473.025ms
VM19742:23 Retrieve from Object: 1469.717ms
VM19742:29 Retrieve from Set: 1666.430ms

As you can see, the set is made a little worse than the object. This bothers me because I thought that the basic implementation would be just the same as the object without the additional overhead of storing values. Does anyone have an additional idea of ​​why this is?

Answer 1

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x = {};
y = new Set();
z = [];

console.time('Insert into Object');
for (var i = 0; i < 1000000; i++) {
    x[i] = 0;
}
console.timeEnd('Insert into Object');

console.time('Insert into Set');
for (i = 0; i < 1000000; i++) {
    y.add(i);
}
console.timeEnd('Insert into Set');

console.time('Insert into Array');
for (i = 0; i < 1000000; i++) {
    z[i] = 0;
}
console.timeEnd('Insert into Array');

var t = 0;

console.time('Retrieve from Object');
for (i = 0; i < 1000000; i++) {
    t = x[i];
}
console.timeEnd('Retrieve from Object');

console.time('Retrieve from Set');
for (i = 0; i < 1000000; i++) {
    t = y.has(i);
}
console.timeEnd('Retrieve from Set');

console.time('Retrieve from Array');
for (i = 0; i < 1000000; i++) {
    t = z[i];
}
console.timeEnd('Retrieve from Array');

console.log(t);

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Insert into Object: 67.558ms
Insert into Set: 259.841ms
Insert into Array: 64.297ms
Retrieve from Object: 19.337ms
Retrieve from Set: 149.968ms
Retrieve from Array: 3.981ms

, ...

:

Insert into Object: 19.103ms
Insert into Set: 40.645ms
Insert into Array: 16.384ms
Retrieve from Object: 40.116ms
Retrieve from Set: 30.672ms
Retrieve from Array: 70.050ms

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Answer 2

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• x.hasOwnProperty(key) x[key]!==undefined.