Test your skills: Loops

MDN Learn
#1

the truth was a bit complicated for me when I had to read the DOM topic
I spent all afternoon trying to do exercise 1 but I don’t realize that I am doing it wrong.
Help xD

See the Pen JavaScript:Loops 1 by lTakisl (@ltakisl) on CodePen.

#2

Hi @Takis :wave:

When you remove the if block around listA.textContent = myArray[i]; your code works. I’m not sure what you wanted to achieve whit this if block, but the result is always false as myArray[i] is a string that gets converted to a number which results in NaN (not a number).

Maybe you could explain what you wanted to achieve and I can clear up the confusion. :slightly_smiling_face:

Michael

#3

I modified it there, thank you! not what happened was the following, as the live exercises in all had to put if () {something;} else {something;}
I assumed it should do the same, and didn’t realize that I had already expressed it with the for () loop. That is why I had tried to put if (myArray [i]> = 0) {that would create the elements li in the ul} ‘’ I think I had put that ‘’, so when going through the elements of the array if the element was greater than or equal a 0 inside the array would print the array element in a li inside the ul.
Something like that hahaha. Now that I put it into words I realize that I made a nice concoction of concepts and things hahaha.

1 Like
#4

Hehe :grin:
Sometimes we think too complicated. Happens to all of us.
You will need if inside for in the next two examples. At least you now know how it works :slightly_smiling_face:

Michael

#5

See the Pen JavaScript: Bucles 2 by lTakisl (@ltakisl) on CodePen.

In the third exercise I did not know how to do so that the loop that I had to do, it will use the isPrime () function so that it will give me as a result the number plus the text is prime in the case that it was. (I think I understand that was what I asked for.)
More or less I managed to get him to tell me what he had to give me but not in the way requested. Enlighten me XD

See the Pen JavaScript: Bucles 3 by lTakisl (@ltakisl) on CodePen.

#6

Task 2 works as expected. Good job!
Small improvement: For objects instead of using “bracket notation” you can mostly use “dot notation” to make it simpler: phonebook[i]['name'] vs. phonebook[i].name

In task 3 you can replace num%2!== 0 with isPrime(num) to make it work. As isPrime() returns true for primes, the if block only gets executed for prime numbers. Below I wrote another solution with a different loop type. As a little bonus exercise you can try to understand it. :slightly_smiling_face:

do {
  if (isPrime(i)) {
    para.textContent += `${i} `;
  }
  i--;
} while (i > 1);

Feel free to ask if you need further help or explanations. Understanding loops is an important part of learning JavaScript. I’m happy to support you.

Happy coding!
Michael

#7

See the Pen JavaScript: Bucles 3 by lTakisl (@ltakisl) on CodePen.

There I modified the exercise and I did it with the do while model. What if I had some doubts.
1.- why using a template literal when putting only the name of the variable does the same gives you the result? for something in particular?
2.- In this case I named the variables’ num ‘but, what if I had wanted to call them’ p ‘? Would I have changed all the’ num ‘to the isPrime function and replaced them with’ p ‘for the code to work with’ p '? including the ‘num’ of isPrime (num) for is Prime § right?

#8

Yep, now it looks good :+1:

  1. I used a template string so I could include the space at the end in the same string. `${i} ` is the same as i + ' '. When you have longer strings with multiple variables it has a better readability, but in this case it doesn’t really matter. In my opinion it just looks more elegant. In your code you mixed template and traditional strings, which I wouldn’t recommend.
  2. You have to change all occurrences of num in and around your loop to p. The num of function isPrime(num) { ... } (parameter and inside of it) is another independent variable and can be left num or changed to whatever other name you like.

I hope my explanations are understandable.

Michael