Group array of strings by first letter-CodePudding

I have this challenge, which consists on:

Writing a function that takes an array of strings as argument
Then, group the strings in the array by their first letter
Return an object that contains properties with keys representing first letters

For example:

Should return

groupIt(['hola', 'adios', 'chao', 'hemos', 'accion'])

// Should return
{ 
 a: [ "adios", "accion" ]
 c: [ "chao" ]
 h: [ "hola", "hemos" ]
}

This is my answer, it returns the expected object, but doesn't pass the test in the page:

function groupIt(arr) {
  let groups = {}
  
  let firstChar = arr.map(el=>el[0])
  let firstCharFilter = firstChar.filter((el,id)=>{
    return firstChar.indexOf(el)===id
  })
 
  firstCharFilter.forEach(el=>{
    groups[el]=[]
  })
  
  firstCharFilter.forEach(char=>{
    for(let word of arr) {
      if(word[0]==char) {
        groups[char].push(word)
      }
    }
  })
    
  return groups
}

groupIt(['hola', 'adios', 'chao', 'hemos', 'accion'])

Where am I failing at?

Here the test: https://www.jschallenger.com/javascript-arrays/javascript-group-array-strings-first-letter

CodePudding user response：

You code is correct, the only wrong part is that you are not lowercasing the first letter, here is your code with additional lowercasing of the first letter, so it passes the test:

function groupIt(arr) {
  let groups = {}
  
  let firstChar = arr.map(el=>el[0])
  let firstCharFilter = firstChar.filter((el,id)=>{
    return firstChar.indexOf(el)===id
  })
 
  firstCharFilter.forEach(el=>{
    groups[el.toLowerCase()]=[]
  })
  
  firstCharFilter.forEach(char=>{
    for(let word of arr) {
      if(word[0]==char) {
        groups[char.toLowerCase()].push(word)
      }
    }
  })
    
  return groups;
}

CodePudding user response：

The site doesn't like .reduce, but here's one way:

const r1 = groupIt(['hola', 'adios', 'chao', 'hemos', 'accion'])
console.log(r1)

// Should return
// {
//   a: ["adios", "accion"]
//   c: ["chao"]
//   h: ["hola", "hemos"]
// }

function groupIt(arr) {
  return arr.reduce((store, word) => {
    const letter = word.charAt(0)
    const keyStore = (
      store[letter] ||     // Does it exist in the object?
      (store[letter] = []) // If not, create it as an empty array
    ); 
    keyStore.push(word)

    return store
  }, {})
}

CodePudding user response：

I ran your code as well as the test examples provided by JS challenger. I noticed that they where case sensitive. So although your code works well, if the words begin with upper case it will not pass certain cases. Attached is my version that passed all test examples.

If you add : .toLowerCase to the firstChar, I believe you will pass as well. Happy coding ;)

P.S if the image below does not work please let me know, I am just learning how to contribute to Stack Exchange, thanks.

const groupIt = (array) => {
  let resultObj = {};
  
  for (let i =0; i < array.length; i  ) {
    let currentWord = array[i];
    let firstChar = currentWord[0].toLowerCase();
    let innerArr = [];
    if (resultObj[firstChar] === undefined) {
       innerArr.push(currentWord);
      resultObj[firstChar] = innerArr
    }else {
      resultObj[firstChar].push(currentWord)
    }
  }
  return resultObj
}

console.log(groupIt(['hola', 'adios', 'chao', 'hemos', 'accion']))

console.log(groupIt(['Alf', 'Alice', 'Ben'])) // { a: ['Alf', 'Alice'], b: ['Ben']}

console.log(groupIt(['Ant', 'Bear', 'Bird'])) // { a: ['Ant'], b: ['Bear', 'Bird']}
console.log(groupIt(['Berlin', 'Paris', 'Prague'])) // { b: ['Berlin'], p: ['Paris', 'Prague']}