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RazerJs
Asked: 2020-09-14 00:29:16 +0800 CST 2020-09-14 00:29:16 +0800 CST

Count the number of characters in a string in javascript

  • 772

I want to make a function that, given a string , counts the number of occurrences of each of its characters . With my function below I contarCaracteresV1()could count a character of the string, but how do I do it for each one? Following a bit the response of @Orici add some things to my function contarCaracteresV2()I see the logic but I have one undefinedof the character that was in uppercase how can I correct this? ... undefinedIt was because the methods I know of for removing repeated characters leave an array with the element ''when they remove a character; I fixed it in my answer contarCaracteresV3() https://es.stackoverflow.com/a/293573/120346

function contarCaracteresV2(str) {
    let caracteres = [... new Set(str.toLowerCase())]

    for(var i=0; i<caracteres.length; i++){
        let arreglo=[]
        str.split('').map(n => {
            if(n.toLowerCase() === caracteres[i]){
                arreglo.push(n)
            } 
            
        })
        console.log(`La cantidad de ${caracteres[i]} es: ${arreglo.length}`);
    }

}

console.log(contarCaracteresV2("Abcaa"));

function contarCaracteresV1(str) {
    let letra = str[0].toLowerCase();
    let arreglo=[]
    str= str.split('');

    str.map(n => {
        if(n.toLowerCase() === letra){
            arreglo.push(n)
        } 
            
    })


    return `La cantidad de ${letra} es: ${arreglo.length}`
}

console.log(contarCaracteresV1("Abcaa"));

javascript

4 Answers

  1. Best Answer

    I would do it the following way.

    1. Remove whitespace and convert the string to lowercase (if necessary)
    2. Loop through the text string instead of passing it to an array.
    3. Finally save the result in an object, where the letter is the key and its total.

    function contarCaracteres(str) {
  //Pasamos la cadena a minusculas(por si lo necesitas)
  //str = str.toLowerCase()
  //quitamos los espacios en blanco
  str = str.replace(/\s/g, "");
  final = {} //Donde guardamos los resultados
  for(let char in str){ //Cogemos el indice de cada caracter
	if(str[char] in final) { //Si ya existe, simplemente aumentamos el contador
		final[str[char]] = final[str[char]] + 1
	} else { // Si no existe, lo inicializamos a 1
		final[str[char]] = 1
    }
}
  //Mostar los resultados
  tmp = ``
  Object.keys(final).forEach(function(letra){
    tmp += `La cantidad de ${letra} es: ${final[letra]} \n`
  })
  return tmp
}
let para_contar = "HOLA hOLA" //Fijate en la h min.
console.log(contarCaracteres(para_contar))

    I hope it helps you.

    • 7

  2. A solution that you could apply is the following:

    • We remove the invisible characters ( eg: str.replace(/\s/g, '') ===> string)
    • We convert the string to an array ( eg: [...string] ==> array)
    • We use reduceto go through the array and pass an object as the second parameter which we will use to store the number of times each letter appears ( eg: obj[char] = obj[char] + 1 || 1)

    Example

    function contarCaracteres(str) {
  return [...str.replace(/\s/g, '')]
    .reduce((obj, char) => {
      obj[char] = obj[char] + 1 || 1;
      return obj;
    }, {});
}

console.log(contarCaracteres("Hola mundo"));

    • 3

  3. Here I am returning each counted character in an object.

    function contarCaracteresV3(str) {
    let cantidadLetras = []
    let caracteres = str.toLowerCase().replace(/ /g, '').split('').filter((c,i,self) => (
        self.indexOf(c) === i
    ))
    
    for(var i=0; i<caracteres.length; i++){
        let arreglo=[]
        str.split('').map(n => {
            if(n.toLowerCase() === caracteres[i]){
                arreglo.push(n)
            }          
        })
        cantidadLetras.push({[caracteres[i]]: arreglo.length})
    }

    return cantidadLetras
}

console.log(contarCaracteresV3("Abcaaa cada"));

    • 2

  4. It can be done by accumulating the number of occurrences of each letter in an array where the index is its ascii code .

    To convert a string to ascii you can use letra.charCodeAt()and to get the opposite String.fromCharCode(codigo):

    function contarCaracteres(cadena) {

    var cont=[];                                  //inicializar el contador
    ncad=cadena.split('');                        //dividir la cadena en caracteres
    for (var i = 0; i < cadena.length; i++) {     //recorrer la cadena
      letra=ncad[i].charCodeAt();                 //pasar cada letra a código ascii
      //antes de sumarlo verificar si ya existe en cont, de no ser así inicializarlo
      cont[letra]==undefined ? cont[letra]=1 : cont[letra]++  
    };
    total={};                                     //para guardar el resultado
    for (var i in cont)                           //recorrer el contador
      total[String.fromCharCode(i)]=cont[i];      //pasar el caracter de ascii a string y pasarle la cantidad
    return total;
  }
  
  console.log(contarCaracteres('aaasddddQQW'));

    This method is case sensitive.

    I hope I have helped to solve the problem, greetings.

    • 2