Capitalize first letter of every other array element

user_9170938 0
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I have an array of elements, ["apple", "cherry", "raspberry", "banana", "pomegranate"], and I want it so that every odd element is capitalized: ["Apple", "cherry", "Raspberry", "banana", "Pomegranate"].

I can capitalize every element in the array, and I can filter out every odd element, but not at the same time (i.e. filtering only shows the odd elements).

Does anyone have any approaches and/or recommendations for this? I've seen questions about capitalizing every other letter, retrieving every other array element, etc., but nothing like what I've asked (yet, I'm still looking).

function alts(arr) {
    const newArr = arr.filter((el, idx) => {
        if (idx % 2 === 0) {
            return arr.map(a => a.charAt(0).toUpperCase() + a.substr(1));
        }
    })
    return newArr;
}

console.log(alts(["apple", "cherry", "raspberry", "banana", "pomegranate"]));
// Just returns [ 'apple', 'raspberry', 'pomegranate' ]

methods arrays algorithm javascript string
4 Answers

Map instead of filtering - inside the callback, if even, return the capitalized portion, else return the original string:

function alts(arr) {
  return arr.map((str, i) => i % 2 === 1 ? str : str[0].toUpperCase() + str.slice(1));
}

console.log(alts(["apple", "cherry", "raspberry", "banana", "pomegranate"]));

user_95152070

You can use a simple for-loop as follows:

function alts(arr=[]) {
  const newArr = [...arr];
  for(let i = 0; i < newArr.length; i+=2) {
    const current = newArr[i];
    if(current)
      newArr[i] = current.charAt(0).toUpperCase() + current.substr(1);
  }
  return newArr;
}

console.log(alts(["apple", "cherry", "raspberry", "banana", "pomegranate"]));

user_74863130

Try this:

function alts(arr) {
    return arr.map((el, idx) => {
        return idx % 2 == 0 ? el.charAt(0).toUpperCase() + el.substr(1) : el;
    })
}

console.log(alts(["apple", "cherry", "raspberry", "banana", "pomegranate"]));

I map through the array and if the element's index is even (that's because index starts from 0, so it's flipped for us as we start counting from 1) then return the element with first letter capitalized, if it's an odd index, then just return the element itself.

user_59112060 

function alts(arr) {
  return arr.map((item, index) => {
    if (index % 2 === 0) {
      return item.charAt(0).toUpperCase() + item.substr(1);
    } else {
      return item
    }
  });
}

console.log(alts(["apple", "cherry", "raspberry", "banana", "pomegranate"]));
// Just returns [ 'apple', 'raspberry', 'pomegranate' ]

user_10422010
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