I want to write a loop for...of which changes the first letter of the day, in the array, to uppercase

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I have my code, I just don’t know how to finish it...

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (day of days) {
console.log(day);
}
javascript

  • https://stackoverflow.com/questions/1026069/how-do-i-make-the-first-letter-of-a-string-uppercase-in-javascript

2 answers

3

If you just want to print, you can use .toUpperCase() and .substr():

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (day of days) {
   console.log(day[0].toUpperCase()+day.substr(1));
}

The day[0].toUpperCase() converts the first letter to uppercase, and the day.substr(1) returns the second character to the end. Then just concatenate the two things.

  • Oops, I fell into the originally presented misleading to title vs code. The answer I removed was based on the susbstring(), could also be the slice(). How would the treatment be in case the element is an Empty string or even a null?

  • We wrote basically the same thing I would just trade the day[o] for substring(0,1) or substr(0,1). This is not the case for the array presented in the question, but because it is a generic string array, some of the elements may be empty or ""

  • Oh yes... then I’d just do an IF: if(day) console.log(day[0].toUpperCase()+day.substr(1));

  • no, it’s the same thing only the edita pro substr(0,1) in place of day[0] because it will not burst error in the case of a ["banana","","maçã"]. Sack?

  • No need, the question does not address this possibility.

1

Another interesting way to achieve the same result is with toUpperCase and slice. The slice serves to get the rest of the string without catching the first letter:

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (day of days) {
  console.log(day[0].toUpperCase() + day.slice(1));
}

Interestingly, he can even do it with a simple regex, which picks up the first letter and replaces it with a capital version at the expense of toUpperCase:

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for (day of days) {
  console.log(day.replace(/\w/, letra => letra.toUpperCase()));
}

The \w of the regex is the one that takes the first letter for processing.

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