Looking to loop over an array to extract certain key-value pairs and append them to an empty object

Question

Looking to loop over an array to extract certain key-value pairs and append them to an empty object

So here's the challenge: create a function that takes an array of strings and outputs an object. The keys in the object should represent the number of characters in each string, while the values should indicate how many times a string with that amount of characters appears.

I hit a roadblock while working on this problem and could really use some assistance. I've tried every search engine query I can think of but haven't had any luck so far. Any help you can provide would be greatly appreciated!

The expected output should resemble this example: characterCount(['apple', 'berry', 'cherry']) // {5:2, 6:1}

function characterCount(arr){

  var newObj = {};
  var valueMax = 0;
  var currentValue = 0;

  for(var i=0; i < arr.length; i++){
    var key = arr[i].length;
    for(var z=0; z < arr.length; z++){
      if (arr[z].length === arr[i].length){
        currentValue ++;
        if (currentValue > valueMax){
          valueMax = currentValue;
        }
      }
    }
    newObj.key = "valueMax";
  }
  return newObj;
}

javascript arrays object

Answer 1

Answer №1

Check out the Array.prototype.reduce method. It allows you to loop through an array, process each value, and produce a single result.

function countCharacters(arr) {
  return arr.reduce((counts, str) => ({
    ...counts,
    [str.length]: (counts[str.length] || 0) + 1
  }), {});
}

const charCounts = countCharacters(['apple', 'berry', 'cherry']);
console.log(charCounts);

Another option is to use Object.assign instead of using the spread operator to merge objects in the accumulator.

function countCharacters(arr) {
  return arr.reduce((counts, str) => Object.assign(counts, {
    [str.length]: (counts[str.length] || 0) + 1
  }), {});
}

const charCounts = countCharacters(['apple', 'berry', 'cherry']);
console.log(charCounts);

Answer 2

Check out the Array.prototype.reduce method. It allows you to loop through an array, process each value, and produce a single result.

function countCharacters(arr) {
  return arr.reduce((counts, str) => ({
    ...counts,
    [str.length]: (counts[str.length] || 0) + 1
  }), {});
}

const charCounts = countCharacters(['apple', 'berry', 'cherry']);
console.log(charCounts);

Another option is to use Object.assign instead of using the spread operator to merge objects in the accumulator.

function countCharacters(arr) {
  return arr.reduce((counts, str) => Object.assign(counts, {
    [str.length]: (counts[str.length] || 0) + 1
  }), {});
}

const charCounts = countCharacters(['apple', 'berry', 'cherry']);
console.log(charCounts);

Answer 3

Answer №2

One way to achieve the desired output is by utilizing the reduce method on the array.

function countCharacters( arr ) {
  return arr.reduce( (agg, current) => {
    // determine length of current item
    const length = current.length;
    // increment value at key index by one (initialize with 0 if it doesn't exist)
    agg[length] = (agg[length] || 0) + 1;
    // return updated object for next iteration
    return agg;
  }, {});
}

console.log( countCharacters(['apple', 'berry', 'cherry']) );

Answer 4

One way to achieve the desired output is by utilizing the reduce method on the array.

function countCharacters( arr ) {
  return arr.reduce( (agg, current) => {
    // determine length of current item
    const length = current.length;
    // increment value at key index by one (initialize with 0 if it doesn't exist)
    agg[length] = (agg[length] || 0) + 1;
    // return updated object for next iteration
    return agg;
  }, {});
}

console.log( countCharacters(['apple', 'berry', 'cherry']) );

Answer 5

Answer №3

While using reduce may be considered more efficient, this code offers a simpler alternative.

function countCharacters(arr) {
  const charactersByLength = {};
  
  for (let item of arr) {
    charactersByLength[item.length] = (charactersByLength[item.length] || 0) + 1;
  }
  
  return charactersByLength;
}

console.log(countCharacters(['apple', 'berry', 'cherry']));

Answer 6

While using reduce may be considered more efficient, this code offers a simpler alternative.

function countCharacters(arr) {
  const charactersByLength = {};
  
  for (let item of arr) {
    charactersByLength[item.length] = (charactersByLength[item.length] || 0) + 1;
  }
  
  return charactersByLength;
}

console.log(countCharacters(['apple', 'berry', 'cherry']));

Looking to loop over an array to extract certain key-value pairs and append them to an empty object

Answer №1

Answer №2

Answer №3

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