flatten-benchmark.js

const { Benchmark } = require("benchmark");
function generateRandomNumberBetween(min, max){
    return Math.floor(Math.random() * max) + min;
}
function generateTupleArray(length) {
    const tupleArray = [];
    for (let i = 0; i < length; i++) {
        tupleArray.push([generateRandomNumberBetween(1, 1e3), generateRandomNumberBetween(1, 1e3)]);
    }
    return tupleArray;
}
// Contains 100 arrays containing elements between 1 and 1000
const arrays = [];
for (let i = 0; i < 100; i++) {
    arrays.push(generateTupleArray(generateRandomNumberBetween(1, 1e3)))
}
const suite = new Benchmark.Suite();
suite.add("acc.concat(curr)", function() {
    for (const arr of arrays) {
        arr.reduce((acc, curr) => acc.concat(curr), []);
    }
});
suite.add("[...acc, ...curr]", function () {
    for (const arr of arrays) {
        arr.reduce((acc, curr) => [...acc, ...curr], []);
    }
});
suite.add("[].concat(...data)", function() {
    for (const arr of arrays) {
        [].concat(...arr);
    }
});
suite.on("cycle", function(event) {
    console.log(String(event.target));
});
suite.on("complete", function() {
    console.log("Fastest is " + this.filter("fastest").map("name"));
})
suite.run();

flatten.js

let arr = [ [1, 2], [3, 4]];
// version 1
arr.reduce((acc, curr) => acc.concat(curr), []);
// version 2
arr.reduce((acc, curr) => [...acc, ...curr], []);
// version 3
[].concat(...arr);

reverse-benchmark.js

const { Benchmark } = require("benchmark");
function generateRandomString(length) {
  var result = "";
  var characters =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  var charactersLength = characters.length;
  for (var i = 0; i < length; i++) {
    result += characters.charAt(Math.floor(Math.random() * charactersLength));
  }
  return result;
}
function generateRandomNumberBetween(min, max){
    return Math.floor(Math.random() * max) + min;
}
// data contains 100 random strings with lneght between 1 and 1000
const data = [];
for (let i = 0; i < 100; i++) {
    data.push(generateRandomString(generateRandomNumberBetween(1, 1000)));
}
const suite = new Benchmark.Suite();
suite.add("string.split()", function() {
    for (const str of data) {
        str.split("");
    }
});
suite.add("Object spread", function () {
    for (const str of data) {
        [...str];
    }
});
suite.add("Array.from()", function() {
    for (const str of data) {
        Array.from(str);
    }
});
suite.on("cycle", function(event) {
    console.log(String(event.target));
});
suite.on("complete", function() {
    console.log("Fastest is " + this.filter("fastest").map("name"));
})
suite.run();

reverse.js

// version 1
"hello".split("").reverse();
// version 2
[..."hello"].reverse();
// version 3
Array.from("hello").reverse();