Tests about inverted index performances on JS arrays

index.js

const linearArray = [];

const testArray = {
  // The array that will hold the values
  array: [],
  // The inverted index
  index: {},
  // The push function
  push: function (value) {
    // Push the value to the array
    this.array.push(value);
    // Save the inverted index
    this.index[value] = this.array.length - 1;
  },
  findIndex: function (value) {
    // Return the value at the inverted index
    return this.index[value];
  },
};

let start, end;

// Fill the array with 1 milion random numbers
start = Date.now();
for (let i = 0; i < 100000; i++) {
  linearArray.push(Math.random());
}
end = Date.now();

console.log(`[LINEAR] Time taken to fill: ${end - start}ms`);

// Fill the testArray with the same values as the linearArray
start = Date.now();
for (let i = 0; i < linearArray.length; i++) {
  testArray.push(linearArray[i]);
}
end = Date.now();

console.log(`[TESTER] Time taken to fill: ${end - start}ms`);

// Testing findIndex in the test array
start = Date.now();
for (let i = 0; i < linearArray.length; i++) {
  // Find the index at the same index in the linearArray
  testArray.findIndex(linearArray[i]);
}
end = Date.now();
console.log(`[TESTER] Time taken to findIndex: ${end - start}ms`);

// Testing findIndex in the linear array
start = Date.now();
for (let i = 0; i < linearArray.length; i++) {
  // Find the index at the same index in the linearArray
  linearArray.findIndex((value) => value === linearArray[i]);
}
end = Date.now();
console.log(`[LINEAR] Time taken to findIndex: ${end - start}ms`);

[LINEAR] Time taken to fill: 45ms
[TESTER] Time taken to fill: 74ms
[TESTER] Time taken to findIndex: 50ms
[LINEAR] Time taken to findIndex: 7147ms