Reversing loop javascript

Question

I have a problem with my exercise. I have to draw something like this: https://screenshots.firefox.com/3qaHB7dcr3n610hi/jsbin.com

And this is my code

  var empty = "";
for(var i=0; i < 5; i++) {
  empty += "*";
  console.log(empty)
}

but with this code I can only make this:

*  
**
***
****
*****

I have no idea how to reverse this loop to start it from top from 5 stars, i tried something like this:

var empty = "";
for (i = 5; i <= 0;i--) {
  empty+="*";
  console.log(empty);
}

But doesn't work. Anybody know how to do this? I will be grateful :)

although that won't change the output since you still start with an empty string — avigil
– avigil, Commented Mar 23, 2018 at 13:59
i changed my condition, but still have problem with the second loop — Kamil Kowalczuk-Fijałkowski
– Kamil Kowalczuk-Fijałkowski, Commented Mar 23, 2018 at 14:01
Stackoverflow isn't a beginner's coding school. You're supposed to exhaust every single other resource first, starting with google. — user5734311
– user5734311, Commented Mar 23, 2018 at 14:03

Ele · Accepted Answer · 2018-03-23 14:07:08Z

2

Your approach builds the first part.
The second part can be accomplished using the function slice in descending direction.

var empty = "";
var i = 0;

// Build the first part
for (; i < 5; i++) {
  empty += "*";
  console.log(empty)
}

// Here i = 5, so this is the initialization for the following loop.
// Loop in descending direction using the function slice.
for (; i > 0; i--) {  
  console.log(empty.slice(0, i))
}

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Mar 23, 2018 at 14:07

answered Mar 23, 2018 at 14:01

Ele

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2 Comments

user5734311 Over a year ago

How is this useful to somebody who cannot construct a for loop?

Shwrk Over a year ago

nice one all the same ;)

yBrodsky · Accepted Answer · 2018-03-23 14:00:33Z

1

Your condition was wrong. Check this.

for(let i = 1; i <= 5; i++) {
  console.log('\"' + '*'.repeat(i) + '\"');
}
for(let i = 5; i > 0; i--) {
  console.log('\"' + '*'.repeat(i) + '\"');
}

answered Mar 23, 2018 at 14:00

yBrodsky

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Comments

Andy · Accepted Answer · 2018-03-23 14:07:05Z

0

Instead of a for/loop you could use a while loop to change the direction:

let stars = 0;
let count = 0;
while (count < 9) {
  if (count < 5) stars++;
  if (count >= 5) stars--;
  const line = Array(stars).fill('*').join('');
  console.log(line);
  count++;
}

answered Mar 23, 2018 at 14:07

Andy

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Comments

theriddle2 · Accepted Answer · 2018-03-23 14:21:47Z

0

Just in case you need a nested for loop. (As some exercises sometimes do)

var k = 0;
for(var i = 1; i < 12; i++){   
    var stx = "";
    for(var j = k; j < i; j++){
        stx += "*";
    }
    if(i > 5) k += 2
    if(i == 6) continue
    console.log(stx);
}

answered Mar 23, 2018 at 14:21

theriddle2

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