Counting the frequency of characters in a string using javascript

Question

I need to write some kind of loop that can count the frequency of each letter in a string.

For example: "aabsssd"

: a: 2, b: 1, s: 3, d: 1

You also need to match the same character as the name of the property in the object. Any good idea how to do this?

I am not sure how to do this.

This is where I am so far:

var arr = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"]; function counter(x) { var count=0, temp = []; x = x.split(''); console.log(x); for(var i=0, len = x.length; i < len; i++) { if(x[i] == "a") { count++; } } return count; } var a = "aabbddd"; console.log(counter(a)); 

Answer 1

Here you go:

 function getFrequency(string) { var freq = {}; for (var i=0; i<string.length;i++) { var character = string.charAt(i); if (freq[character]) { freq[character]++; } else { freq[character] = 1; } } return freq; }; 

Answer 2

some ES6 syntax with reduction:

 let counter = str => { return str.split('').reduce((total, letter) => { total[letter] ? total[letter]++ : total[letter] = 1; return total; }, {}); }; counter("aabsssd"); // => { a: 2, b: 1, s: 3, d: 1 } 

Answer 3

Another solution:

 function count (string) { var count = {}; string.split('').forEach(function(s) { count[s] ? count[s]++ : count[s] = 1; }); return count; } 

Answer 4

A more declarative way to get a histogram of words would be to use abbreviation to repeat letters and create a new object that contains letters as keys and frequencies as values.

 function getFrequency(str) { return str.split('').reduce( (prev, curr) => { prev[curr] = prev[curr] ? prev[curr] + 1 : 1; return prev; }, {}); }; console.log(getFrequency('test')); // => {t: 2, e: 1, s: 1} 

Answer 5

Here is another option using underscore.js:

 function charCount(str) { return _(str.split('')).countBy(function(char) { return char.toLowerCase(); }); } 

charCount('aaabbbbdd') outputs Object {a: 3, b: 4, d: 2}

Answer 6

 for(i = strlen(string)var string = 'aabsssd'; var chars = new Array(); for(var i = 0; i < string.length; i++){ var char = string.charAt(i); if(chars[char] == undefined){ chars[char] = 0; } chars[char]++; } console.log(chars); 

Answer 7

  const recorrences = ['a', 'b', 'c', 'a', 'b','a'] .map(i => !!~i.indexOf('a')) .filter(i => i) .length; console.log(`recorrences ${recorrences}`) //recorrences 3 

Answer 8

Here is another way:

 const freqMap = s => [...s].reduce((freq,c) => {freq[c] = -~freq[c]; return freq} ,{}) 

Or, if you prefer the "for" loop:

 function freqMap(s) { freq={}; for (let c of s) freq[c]=-~freq[c]; return freq; } 

for example, freqMap ("MaMaMia") returns an object {M: 3, a: 3, i: 1}

This method uses the fact that in javascript, bitwise not at "undefined" it gives -1, while "undefined + 1" gives NaN). So, - ~ undefined is 1, - ~ 1 is 2, - ~ 2 is 3, etc.

Thus, we can iterate over the characters of a string and simply increment freq [c] without any "if". The first time we encounter the character c, freq [c] will be undefined, so we set it to - ~ freq [c], which is 1. If we subsequently meet c again, we will set freq [c] to again - ~ freq [c], which will now be 2, etc.

Simple, elegant, concise.

Answer 9

simpler and more functional solution:

using arrows ES6 & Logical operators:

 const buildFreqDict = string => string.split('').reduce((freqDict, char) => { freqDict[char] = (freqDict[char] || 0) + 1; return freqDict; }, {}) console.log(buildFreqDict("banana")) 

Explanation

• split a string into an array of characters.
  • and then pass it to the Reduce method (using method.chaining ()).
• if char is already in countDict, then add 1 to it.
  • or if the character is not found in countDict, set it to 1.
• return new values ​​back to reduce the storage object
• NB: do not forget to include the third argument .reduce () : in this case it is {} (object literal), which serves to initialize the freqDict object.

for more information, see Counting value instances in an object halfway down the page: MDN Reduce
and for more information on using logical operators, see here: MDN Logical Operators.

Answer 10

 // Count frequency of characters in a string // input: 'Hello, I'm Paul!' // result: { // H: 1, // E: 1, // L: 3, // ... and so on ... // } const countChars = (string) => { let charStats = {}; string = string.replace(' ', '').toUpperCase().split(''); string.forEach((char) => { if (charStats[char]) { charStats[char]++; } else { charStats[char] = 1; } }); return charStats; }; 

Answer 11

Another solution

  function maxChar(str) { const charMap = {}; let max = 0; let maxChar = ''; for(let char of str){ if(charMap[char]){ charMap[char]++; }else{ charMap[char] = 1; } } for(let char in charMap){ if(charMap[char] > max){ max = charMap[char]; maxChar = char; } } return maxChar; } 

===>

  maxChar('355385') "5" 

Answer 12

 var str = 'abcccdddd'; function maxCharCount(target) { const chars = {}; let maxChar = ''; let maxValue = 1; for (let char of target) { chars[char] = chars[char] + 1 || 1; } return chars; } console.log(maxCharCount(str)); 

Answer 13

The same solution, but refactoring. It's great that we can solve this problem with a lot of different answers :)

 function getFrequency(string) { var freq = {}; for (let character in string) { let char = string[character]; (freq[char]) ? freq[char]++ : freq[char] = 1 } return freq; }; 

Answer 14

You can use this. Just pass the string and it will return the object with all the frequency of characters.

 function buildCharMap(string) { const charMap = {}; string.replace(/[^\w]/g, '').toLowerCase(); for (let char of string) { charMap[char] = charMap[char] + 1 || 1; } return charMap; } 

Answer 15

Cheat code for counting the frequency of a character in a string

 let target = "e"; let string = " i want to see that person that came in here last"; let frequency = string.split(target).length; 

or all in one line

 console.log(string.split("e").length) 

Answer 16

The Easy Way In addition, you will get an alphabetically sorted list. It passes through the array and evaluates whether the symbol is already in the object: if false, the symbol is added to the object, if true, its frequency increases by one.

 const text= "Lorem ipsum dolor sit amet consectetur adipiscing" const textAsArray = text.split('').sort() let charactersList = {} for (char of textAsArray) { if (!charactersList[char]) { charactersList[char]=1; } else { charactersList[char]++ } } console.log(charactersList) 

Answer 17

I have reviewed and think that it adapts very well to the needs that they represent. I would like it to be on the same line, but I don’t know how to generate the object dynamically.

 const uniqueCount=(arr)=>{ let rs ={}; arr.sort().join("").match(/(.)(\1*)/g).map(i=>rs[i[0]]=i.length); return rs; }; console.log(uniqueCount(["a","b","c","d","d","e","a","b","c","f","g","h","h","h","e","a"])); //{ a: 3, b: 2, c: 2, d: 2, e: 2, f: 1, g: 1, h: 3 } 

I find it very successful to use .match() and regular expressions /(.)(\1*)/g as described above.

If it's just a string, you just need to add .split("") before that and that’s it.