Given an array of strings, write a function that returns an array of objects representing each unique string and its frequency in the original array

I want to print the string and the frequency of it as an object stored inside an array. I have been using only reduce method to do so and want result through the same method only, Can anyone tell me what should I rectify in the below code:

const strings = ["pink", "red", "pink", "yellow", "yellow", "yellow"];

const frequencyOfStrings = (arrayOfStrings) => {
  return arrayOfStrings.reduce((acc, curr) => {
    if (acc[curr]) {
      acc[curr]++;
    } else {
      acc[curr] = 1;
    }
    return acc;
  }, []);
};

console.log(frequencyOfStrings(strings));

I am getting output as:

[ pink: 2, red: 1, yellow: 3 ]

Whereas I want my output as:

[{ string: 'pink', frequency: 2 }, { string: 'red', frequency: 1 }, { string: 'yellow', frequency: 3 }]

P.S - I am a beginner at Javascript with no knowledge of time-complexities, as of now.

To achieve the desired output format, you need to modify the reduce function to return an array of objects instead of an object.
Here is the updated code

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

const strings = ["pink", "red", "pink", "yellow", "yellow", "yellow"];

const frequencyOfStrings = (arrayOfStrings) => {
  return Object.entries(
    arrayOfStrings.reduce((acc, curr) => {
      if (acc[curr]) {
        acc[curr]++;
      } else {
        acc[curr] = 1;
      }
      return acc;
    }, {})
  ).map(([string, frequency]) => ({ string, frequency }));
};

console.log(frequencyOfStrings(strings));

<!-- end snippet -->

It's better to use a foreach to do the job, but you can use reduce and you need to change the logic inside it.

In your desired output you want an array of objects, so inside your reduce, you need to look for the right object in your output array then update its frequency, if it matches your current element, otherwise add a new element with 1 as frequency.

This is how should be your code:

const frequencyOfStrings = (arrayOfStrings) => {
  return arrayOfStrings.reduce((acc, curr) => {
    let foundIndex = acc.findIndex(el => el["string"] === curr);
    if (foundIndex >= 0) {
      acc[foundIndex].frequency++;
    } else {
      acc.push({
        "string": curr,
        "frequency": 1
      })
    }
    return acc;
  }, []);
};

Demo:

<!-- begin snippet: js hide: true console: true babel: false -->

<!-- language: lang-js -->

const strings = ["pink", "red", "pink", "yellow", "yellow", "yellow"];

const frequencyOfStrings = (arrayOfStrings) => {
  return arrayOfStrings.reduce((acc, curr) => {
    let foundIndex = acc.findIndex(el => el["string"] === curr);
    if (foundIndex >= 0) {
      acc[foundIndex].frequency++;
    } else {
      acc.push({
        "string": curr,
        "frequency": 1
      })
    }
    return acc;
  }, []);
};

console.log(frequencyOfStrings(strings));

<!-- end snippet -->

Why do you insist on using a tool (reduce) which is obviously not appropriate for the job? Just use a loop:

const frequencyOfStrings = (arrayOfStrings) => {
    let m = new Map

    for (let string of arrayOfStrings)
        if (m.has(string))
            m.get(string).frequency += 1
        else
            m.set(string, {string, frequency: 1})

    return [...m.values()]
}