Problem with Function return values active learning

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1

Hi, i am working in to example active learning of function return values( https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Return_values) github repository(https://github.com/mdn/learning-area/blob/master/javascript/building-blocks/functions/function-library-finished.html), and i try to add a new function square Root but it does not work, please can you help me ?.

function squaredRoot(num = null) {

let contador = 0;

  for (let i = 1; i<= num; i++){

    contador++;

    if((contador*contador) === num){

      break;

    }

  }


  return contador;

}

//this is the easy way and is perfectly functional in the console and event onchange.

function squaredRoot2(num = null) {

  return Math.sqrt(num);

}

//in the console the function squareRoot is functional, but in the event onchange does not work, why?

input.onchange = function() {

  let num = input.value;

  if (isNaN(num)) {

    para.textContent = 'You need to enter a number!';

  } else {

    para.textContent = num + ' squared is ' + squared(num) + '. ' +

                      num + ' cubed is ' + cubed(num) + '. ' +

                      num + ' square root is ' + squaredRoot(num) + '. ' +

                      num + ' factorial is ' + factorial(num) + '.';
  }
}
2

Hi @Matias_Concha and welcome to the community :wave:

At a first glance I only see a problem when using a number which doesn’t have a integer root (like 24). Since the multiplication in your function could never reach it.

To make it easier could you please put your code in an online editor like https://codepen.io and tell us what exactly doesn’t work as expected.

Thank you very much and have a nice day!
Michael

3

Hi @mikoMK Thank you for such a nice words, this is the codepen link https://codepen.io/falling-skx/pen/xxrOoWN . When i put in the input the number 4 for example, it does not work like i expect, if you have an idea please let me know.

4

Thanks for the Pen, @Matias_Concha
Now I see the problem. Everything from an input field is a string. It doesn’t matter with the other functions since they automatically convert the string into an integer. In your function you are using the strict equality operator (===) which also checks the type. Since it is comparing an integer to a string it is always false and the loop never breaks.

You have several possibilities to solve this problem:

  • Parse the string in the onchange function:
    let num = parseInt(input.value, 10);
  • Parse the string in your function:
    if((contador*contador) === parseInt(num, 10){
  • Use the unary plus operator in your function:
    if((contador*contador) === +num){
  • Use the (non-strict) equality operator:
    if((contador*contador) == num){

I recommend the first method since we want to work with integers in all functions. You should never use the last method unless there is no other way.

If you have any more questions I’m happy to help :slightly_smiling_face:
Michael

1 Like
5

Wow!!!, i broke my head with this exercise and the solution is very simple, i have a lot to learn, thanks you very much for your time and your explanation.

1 Like