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How to use the countBy function from lodash

Find comprehensive JavaScript lodash.countBy code examples handpicked from public code repositorys.

lodash.countBy is a method provided by the Lodash library used to create an object with the count of occurrences of each element in an array.

astrobench.js

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* @example
*
* _.countBy([4.3, 6.1, 6.4], function(num) { return Math.floor(num); });
* // => { '4': 1, '6': 2 }
*
* _.countBy([4.3, 6.1, 6.4], function(num) { return this.floor(num); }, Math);
* // => { '4': 1, '6': 2 }
*
* _.countBy(['one', 'two', 'three'], 'length');
* // => { '3': 2, '5': 1 }

711

+ 5 other calls in file

lodash-contrib.commonjs.js

GitHub: node4good/lodash-contrib

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module.exports.cond                = _.cond;
module.exports.conforms            = _.conforms;
module.exports.conjoin             = _.conjoin;
module.exports.cons                = _.cons;
module.exports.constant            = _.constant;
module.exports.countBy             = _.countBy;
module.exports.create              = _.create;
module.exports.curry               = _.curry;
module.exports.curry2              = _.curry2;
module.exports.curry3              = _.curry3;

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+ 92 other calls in file

How does lodash.countBy work?

lodash.countBy is a method provided by the Lodash library used to create an object with the count of occurrences of each element in an array. When lodash.countBy is called with an array and an iteratee function, it iterates over each element in the array and applies the iteratee function to each element. The iteratee function is used to transform each element into a key that will be used in the resulting object. For example, if the iteratee function returns the first letter of each element, lodash.countBy will return an object with the count of occurrences of each letter in the array. By default, lodash.countBy counts the occurrences of each element in the array. However, it also accepts a second argument, which is a function that can be used to customize the count calculation. This function takes two arguments: the current count and the value of the current element. It should return the updated count. For example, if we wanted to count the occurrences of even and odd numbers in an array, we could use lodash.countBy with a custom function to update the count for each element based on whether it is even or odd. By using lodash.countBy, we can easily create an object with the count of occurrences of each element in an array and use it for further analysis or processing. Note that lodash.countBy assumes that the input array is not sorted. If the input array is sorted, the result of calling this method is undefined.

index.js

GitHub: sluukkonen/iiris

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    const iirisCallback = (x) => String(x % 10)
    const lodashCallback = (x) => String(x % 10)
    const ramdaCallback = (x) => String(x % 10)
    return {
      iiris: () => A.countBy(iirisCallback, array),
      lodash: () => _.countBy(array, lodashCallback),
      ramda: () => R.countBy(ramdaCallback, array),
    }
  },
},

update.js

GitHub: UniversityOfHelsinkiCS/palaute

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  return _.uniq(currentIds).filter(Number)
}


const validateGroupingQuestions = questions => {
  const tooManyGroupingQuestions = _.countBy(questions, 'secondaryType').GROUPING > 1
  if (tooManyGroupingQuestions) ApplicationError.BadRequest('Maximum of one grouping question is allowed')


  const illegalGroupingQuestion = questions.some(
    q => q.secondaryType === 'GROUPING' && !['SINGLE_CHOICE', 'MULTIPLE_CHOICE'].includes(q.type)

Ai Example

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const _ = require("lodash");

const words = ["apple", "banana", "cherry"];
const letterCount = _.countBy(words, (word) => word[0]);

console.log(letterCount);
// Output: { 'a': 1, 'b': 1, 'c': 1 }

In this example, we first import the Lodash library using the require function. We then define an array of strings and call _.countBy with this array and a callback function that takes each string as input and returns the first letter of that string. The resulting object contains a count of how many times each letter appeared as the first letter of a string in the words array. In this case, each letter appears only once as the first letter of a string, so the resulting object contains the count of 1 for each letter. Finally, we log the resulting object to the console. By using lodash.countBy, we can easily count the number of occurrences of each element in an array and use the resulting object for further analysis or processing.

lodash.js

GitHub: mdmarufsarker/lodash

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console.log(zipWith); // => [111, 222]




// Collection


const countBy = _.countBy([6.1, 4.2, 6.3], Math.floor);
console.log(countBy); // => { '4': 1, '6': 2 }


const each = _.each([1, 2], value => console.log(value));

+ 15 other calls in file

wechat.js

GitHub: dgodance/Wechat-Admin-API

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* 微信用户登出
*/
async chart() {

  let data = await this.friends({});
  let sexData = _.countBy(data, 'gender');
  let provinceData = _.countBy(data, 'province');
  return { sexData, provinceData }

core.js

GitHub: frlender/Jandas

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    if (ascending === void 0) { ascending = true; }
    var idx = (0, df_lib_1._sortIndices)(this.values, ascending);
    return this.iloc(idx);
};
Series.prototype.value_counts = function () {
    var obj = _.countBy(this.values);
    var pairs = _.toPairs(obj);
    var df = new DataFrame(pairs, null, ['value', 'count']);
    return df.sort_values('count', false);
};

list_helper.js

GitHub: rtapper1/fullstackopen2022

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const mostBlogs = (blogs) => {
  if (blogs.length === 0) {
    return undefined
  }
  
  const authorBlogs = _.countBy(blogs, (blog) => blog.author)
  const mostBlogsAuthor = _.maxBy(Object.entries(authorBlogs), (author) => author[1])
  return  {author: mostBlogsAuthor[0], blogs: mostBlogsAuthor[1]}
}

list_helper.js

GitHub: Gefferson-Souza/Part-4

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const mostBlogs = (listOfBlogs) => {
    if(!listOfBlogs){
        return 0
    }


    const count = _.countBy(listOfBlogs, (e) => e.author)


    const author = Object.keys(count) 
    const blogs = Object.values(count)

+ 3 other calls in file

list_helper.js

GitHub: edzhuks/full-stack-open

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  return mostPopularBlog
}


const mostBlogs = (blogs) => {
  const counts = _.countBy(blogs, 'author')
  const countsAsTuples = _.entries(counts)
  const maxTuple = _.maxBy(countsAsTuples, _.last)


  if(maxTuple === undefined){

index.js

GitHub: gitonga123/jest-level-up

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    return res.status(503).send({ success: false, message: 'Something Went Wrong' });
  }


});


const countOccurrence = (str, ch) => _.countBy(str)[ch] || 0;


app.get("/api/update/players/form", async (req, res) => {
  try {
    let last_id = 119549;

util.js

GitHub: SolidZer0/SolidZer0.github.io

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module.exports = {
  // Control if deck is legit
  // => all the deck's cards appear in players pool
  deck(deck, pool) {
    const poolByName = countBy(pool, ({name}) => name);


    for (const zoneName in deck) {
      const zone = deck[zoneName];
      for (let cardName in zone) {

list_helper.js

GitHub: stylized-substance/Full-Stack-open-2022

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  return [mostLikedBlog, mostLikedBlogFiltered];
};


const mostBlogs = (inputBlogs) => {
  const { author } = _.maxBy(inputBlogs, 'author');
  const blogsCount = _.countBy(inputBlogs, 'author');
  const blogs = _.max(Object.values(blogsCount));
  return { author, blogs };
};

list_helper.js

GitHub: ihamuma/fullStackOpen

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}


// Return the author with the most blogs and how many blogs they've written
const mostBlogs = (blogs) => {
    // Count the amount of times an author appears. countBy returns an object with author names as keys and the amount of blogs they've written
    const authorBlogs = lodash.countBy(blogs, 'author')
    // Find author with most blogs. maxBy takes author names and function that returns value to max (amount of blogs)
    const maxBlogsAuthor = lodash.maxBy(lodash.keys(authorBlogs), author => authorBlogs[author])
    // Finally, total blogs of author with most blogs
    const maxBlogsCount = authorBlogs[maxBlogsAuthor]

list_helper.js

GitHub: Mimi-codes/fullstackopen

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};


const mostBlogs = (blogs) => {
  if (blogs.length === 0) return null;


  const authorCount = lodash.countBy(blogs, "author");


  const topAuthor = Object.keys(authorCount).reduce((a, b) => {
    return authorCount[a] > authorCount[b] ? a : b;
  });

list_helper.js

GitHub: ahmed751995/fs-part4

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  return favPost;
};


const mostBlogs = (blogs) => {
  const authors = _.countBy(blogs, 'author');
  let mostAuth = {blogs: 0};
  
  for(let author in authors) {
    if(authors[author] > mostAuth.blogs) {

list_helper.js

GitHub: yingtu35/full-stack-open-exercises-4

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const mostBlogs = (blogs) => {
    if (blogs.length === 0) {
        return null
    }
    const blogsCount = _.countBy(blogs, (blog) => blog.author)
    const blogsCountEntries = Object.entries(blogsCount)
    const maxBlogsAuthor = blogsCountEntries.reduce((acc, array) => array[1] > acc[1] ? array : acc)
    const res = {
        author: maxBlogsAuthor[0],

list_helper.js

GitHub: hjarve/fullstackopen

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const mostBlogs = (blogs) => {
    if (blogs.length === 0) {
        return 0;
    }
    let authors = _.countBy(blogs, function(blog) { return blog.author});
    authors = _.toPairs(authors);
    let mostBlogsAuthor = authors[0];
    for(let author of authors){
        if ( author[1] > mostBlogsAuthor[1] ) {

list_helper.js

GitHub: mbilly7/Blog-App

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if (blogs.length === 0) {
  return mostBlogsResult;
}

const authorBlogs = _.countBy(blogs, 'author');

// eslint-disable-next-line no-restricted-syntax
for (const [author, numberOfBlogs] of Object.entries(authorBlogs)) {
  if (numberOfBlogs > mostBlogsResult.blogs) {

list_helper.js

GitHub: rafaeltxc/Helsinki-Challenge

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  const json = arrList.find((unit) => unit.likes === mostLikes);
  return (({ title, author, likes }) => ({ title, author, likes }))(json);
}


function authorWithMoreBlogs(arrList) {
  const authorsBlogs = _.countBy(arrList, (unit) => unit.author);
  const formatedJson = _.map(authorsBlogs, (nbBlog, authorName) => {
    return {
      author: authorName,
      blogs: nbBlog,

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