JS Code: Develop a function that generates a distribution analysis of an array

Question

JS Code: Develop a function that generates a distribution analysis of an array

I have been working on a function that calculates the frequency distribution of an array. The aim is to output an object in which the keys represent the unique elements and the values show how frequently those elements appear.

Here's the code I've written so far:

function getFrequencies(arr) {

  let obj = {}; 

  for (let i=0; i<arr.length; i++){
    let element = arr[i]; 

    console.log(element)

    // check if key exists in the object already

    // if it does, increment its value by 1
    if (obj[element] !== undefined){
      obj[element] += 1;
    }

    // if it doesn't, set the initial value to 1
    else {
      obj[element] === 1; 
    }
  }
  return obj
}

Upon calling getFrequencies(["A", "B", "A", "A", "A"]), my current code gives an empty object instead of the expected result:

{ A: 4, B: 1 }

I'm wondering what errors might be present in my implementation?

javascript arrays object if-statement count

Answer 1

Answer №1

obj[element] === 1; this is comparing values, not assigning them.

To assign a value of 1 to obj[element], use the syntax: obj[element] = 1;

An easier way to achieve this in ES6+ is:

arr.reduce((acc, item) => {
  acc[item] = (acc[item] || 0) + 1;
  return acc;
}, {});

Answer 2

obj[element] === 1; this is comparing values, not assigning them.

To assign a value of 1 to obj[element], use the syntax: obj[element] = 1;

An easier way to achieve this in ES6+ is:

arr.reduce((acc, item) => {
  acc[item] = (acc[item] || 0) + 1;
  return acc;
}, {});

Answer 3

Answer №2

The issue in your code is that you are using equality instead of assignment in the else part.

obj[element] === 1;

You should change it to

obj[element] = 1;

This way, your code will properly initialize keys on obj

function calculateFrequencies(inputArr) {
  let obj = {};
  for (let i = 0; i < inputArr.length; i++) {
    let element = inputArr[i];
    if (obj[element] !== undefined) {
      obj[element] += 1;
      console.log(obj, 'inside if')
    }
    else {
      obj[element] === 1;
      console.log(obj, 'inside else')
    }
  }
  return obj
}

console.log(calculateFrequencies(["A", "B", "A", "A", "A"]));

An alternative approach is to use the reduce method

function calculateFrequencies(inputArr) {
  return inputArr.reduce((result, item) => {
    result[item] = result[item] || 0;
    result[item]++;
    return result;
  },{});
}

console.log(calculateFrequencies(["A", "B", "A", "A", "A"]));

Answer 4

The issue in your code is that you are using equality instead of assignment in the else part.

obj[element] === 1;

You should change it to

obj[element] = 1;

This way, your code will properly initialize keys on obj

function calculateFrequencies(inputArr) {
  let obj = {};
  for (let i = 0; i < inputArr.length; i++) {
    let element = inputArr[i];
    if (obj[element] !== undefined) {
      obj[element] += 1;
      console.log(obj, 'inside if')
    }
    else {
      obj[element] === 1;
      console.log(obj, 'inside else')
    }
  }
  return obj
}

console.log(calculateFrequencies(["A", "B", "A", "A", "A"]));

An alternative approach is to use the reduce method

function calculateFrequencies(inputArr) {
  return inputArr.reduce((result, item) => {
    result[item] = result[item] || 0;
    result[item]++;
    return result;
  },{});
}

console.log(calculateFrequencies(["A", "B", "A", "A", "A"]));

Answer 5

Answer №3

Within your else section, ensure you are performing assignment instead of strict comparison, like so:

obj[element] = 1;

Rather than:

obj[element] === 1;

Take a look at the functional demonstration provided below:

function calculateOccurrences(array) {

  let obj = {}; 

  for (let i=0; i<array.length; i++){
    let element = array[i]; 

    console.log(element)

    // Check if key already exists in object

    // If it does, increment the value by 1
    if (obj[element] !== undefined){
      obj[element] += 1;
    }

    // If it doesn't exist, assign 1 to initialize future elements
    else {
      obj[element] = 1; 
    }
  }
  return obj
}

console.log(calculateOccurrences(["A", "B", "A", "A", "A"]));

Answer 6

Within your else section, ensure you are performing assignment instead of strict comparison, like so:

obj[element] = 1;

Rather than:

obj[element] === 1;

Take a look at the functional demonstration provided below:

function calculateOccurrences(array) {

  let obj = {}; 

  for (let i=0; i<array.length; i++){
    let element = array[i]; 

    console.log(element)

    // Check if key already exists in object

    // If it does, increment the value by 1
    if (obj[element] !== undefined){
      obj[element] += 1;
    }

    // If it doesn't exist, assign 1 to initialize future elements
    else {
      obj[element] = 1; 
    }
  }
  return obj
}

console.log(calculateOccurrences(["A", "B", "A", "A", "A"]));

JS Code: Develop a function that generates a distribution analysis of an array

Answer №1

Answer №2

Answer №3

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