Why does i+=1 double the output of i+=2?

Question

I'm confused. Why does i+=1 in the following block of code print the output 12x, but i+=2 only prints it 6 times? Shouldn't it be the other way around? (My brain isn't working today.)

function printManyTimes(str) {
  "use strict";

  const SENTENCE = str + " is cool!";

  for (let i = 0; i < str.length; i += 2 ) {
    console.log(SENTENCE);
  }
}

printManyTimes("freeCodeCamp");

Which set has more members `{ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 }` or `{2, 4, 6, 8, 10, 12}`? — VLAZ, Oct 22 '19 at 16:28
Are you asking why it takes 12 times to get to a number with 1 while counting by 2 it takes 6 times??? — epascarello, Oct 22 '19 at 16:32

score 4 · Answer 1 · answered Oct 22 '19 at 16:25

4

It loops while i is less than str.length.

If you increase i twice as quickly, then it becomes as long as str.length in half the time.

answered Oct 22 '19 at 16:25

Quentin

914,110
126
1,211
1,335

score 2 · Answer 2 · answered Oct 22 '19 at 16:25

2

Because you are advancing the iterator two units per each iteration

answered Oct 22 '19 at 16:25

jperelli

6,988
5
50
85

score 0 · Answer 3 · answered Oct 22 '19 at 16:31

Here is a modified version of your code to show how a for loop works. Quentin's answer explains it pretty well.

function printManyTimes(str, amountToIncrement) {
  "use strict";

  const SENTENCE = str + " is cool!";

  for (let i = 0; i < str.length; i += amountToIncrement ) {
    console.log(SENTENCE + " " + i);
  }
}

console.log("increment amount as 1")
printManyTimes("freeCodeCamp", 1);

console.log("increment amount as 2")
printManyTimes("freeCodeCamp", 2);

console.log("increment amount as 3")
printManyTimes("freeCodeCamp", 3);

console.log("increment amount as .5")
printManyTimes("freeCodeCamp", .5);

score 0 · Answer 4 · answered Oct 22 '19 at 17:00

function printManyTimes(str) {
  "use strict";

  const SENTENCE = str + " is cool!"; // freeCodeCamp is cool!

  for (let i = 0; i < str.length; i += 2 ) { 
    // if i+=2 in your loop the console log run only while i = [0, 2, 4, 6, 8, 10] - 6 times
    // if i+=1/i++ in your loop the console log run only while i = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] - 12 times
    console.log(SENTENCE);
  }
}

printManyTimes("freeCodeCamp"); // freeCodeCamp length = 12

it's a basic knowledge of arrays. You can find more information in https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

Why does i+=1 double the output of i+=2?

4 Answers4