Which is more performant array.includes or string.includes?

Question

I am trying to find out which is more performant:

let array = [1,2,3,4]
array.includes(4)

or

let str = "1234";
str.includes(4);

and have tried to find it out by executing:

console.time();
let ar = [1,2,3,4,5];
ar.includes(4);
console.timeEnd();

console.time();
let str = "12345";
str.includes("4");
console.timeEnd();

in the console and from a script within the page. When directly executing from the console, the times are such that array.includes takes the least time. When executing from a page, the times reported are such that string.includes takes less time. What gives?!

Answer 1

With small number of values to test against:

• On Benchmark Suite: https://jsfiddle.net/533hc71h/464/
• On Node:
• On Chrome console:

Conclusion: array.includes is faster than string.includes

Then I tried increasing the number of values to ~100:

• On Benchmark Suite: https://jsfiddle.net/533hc71h/465/
• Node
• Chrome console:

Ended up with same results: array.includes is faster than string.includes

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If you are interested in the implementation algorithm you can look at it here:

• Array includes: http://www.ecma-international.org/ecma-262/7.0/#sec-array.prototype.includes
• String includes: https://tc39.github.io/ecma262/#sec-string.prototype.includes

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PS: In your case, I think the variable declaration is taking more time in Array Incldues test than string declaration. If you move the declaration out of the timer, you should also see consistent results.

Proof:

String declaration takes 1/10th the time that it takes to declare an array