Searching for power of 2

beatriju0572531286 · December 19, 2020, 10:33am

gist.github.com

https://gist.github.com/codecademydev/ae986e50c18c13438fcf3f11ed417a1c

main.js

const numbers = [5, 3, 9, 30];

const smallestPowerOfTwo = arr => {
      let results = [];
      // The 'outer' for loop - loops through each element in the array
      for (let i = 0; i < arr.length; i++) {
            number = arr[i];

            // The 'inner' while loop - searches for smallest power of 2 greater than the given number
            let j = 1;

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Heyy, could someone explain me, please, why power of 2 written this way? It doesn’t make sense for me why it’s j=j*2…

mike7127143742 · December 19, 2020, 12:54pm

            let j = 1;
            while (j < number) {
                  j = j * 2;
            }

The powers of two are 1, 2, 4, 8, 16, 32, 64, 128… and so on (doubling in the sequence). The line j = j * 2 is inside the while loop. It doubles j and assigns this new value to j every time the loop executes. So initially j = 1. Then this line executes:

j = j * 2.

After this j is assigned the value of 2. Next time in the loop j will be 4 and so on until the condition of the while loop (j < number) is no longer true. At this point the correct j value is “found” and it is entered into the array when while loop stops. You can also enter a console.log(j) inside the while loop to see what is happening as it can help with debugging and understanding.