How to join strings in a for loop in Javascript?-CodePudding

I am trying to capitalise the first character of each word and join all words into one string. I have managed to capitalise the first character of each word but cant seem to get .join() to work on the final result

function generateHashtag (str) {

 let split = str.split(' ')

 for(let i = 0; i < split.length; i  ){

  let finalResult = split[i].charAt(0).toUpperCase()   split[i].substring(1)

   console.log(finalResult.join(''))

  }


}

console.log(generateHashtag('Hello my name is')) should return ('HelloMyNameIs')

CodePudding user response：

Achieving this by split is possible. first create an array of divided strings (by the delimiter ' ') and then loop around the array and capitalize the first char using the method toUpperCase and concat the rest of the string without the first letter using slice

function generateHashtag(str) {
  let split = str.split(' ');
  for (let i = 0; i < split.length; i  ) {
    split[i] = split[i].charAt(0).toUpperCase()   split[i].slice(1);
  }
  return split.join('');
}

console.log(generateHashtag('Hello my name is'));

More about split - https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/split

CodePudding user response：

you can do split[i] = split[i].charAt(0).toUpperCase() split[i].substring(1) in the loop then outside loop do split.join('')

Basically you are replacing each word (split[i]) with capitalised word. Then in the end join the words.

CodePudding user response：

finalResult is a String, not an Array so there is no join function.

Use this instead :

function generateHashtag (str) {

 let arrayWords = str.split(' ')
 const titleCasedArray = arrayWords.map(word => titleCaseWord(word))
 return titleCasedArray.join('');

}

function titleCaseWord (word){
  return word.slice(0,1).toUpperCase()   word.slice(1,-1).toLowerCase()

}

CodePudding user response：

You can do something like this:

function generateHashtag (str) {
  //returns array of strings
  let split = str.split(' ') 
  //returns array of strings with each word capitalized
  const capitalizedWordsArr = split.map( word => word.charAt(0).toUpperCase()   word.substring(1))
  //returns a string by joining above array with no spaces
  return capitalizedWordsArr.join('') 
}

CodePudding user response：

This is a perfect use-case for Array.prototype.reduce:

function generateHashtag(str) {
  return str
    .split(' ')
    .reduce((acc, [firstLetter, ...rest]) => acc  = `${firstLetter.toUpperCase()}${rest.join('')}`,
    ''
  );
}
console.log(generateHashtag('Hello my name is')); // should return ('HelloMyNameIs')

CodePudding user response：

Javascript strings are immutable so you cannot overwrite them on the go, but you can overwrite array elements.

By using String.prototype.substr() you can extract a part of the string, you can use these parts, modify it and create a new string then replace the old array element. finally returning the joined string like you wanted to

function generateHashtag(str) {

    const split = str.split(' ') // array of words

    for (let i = 0; i < split.length; i  )
        split[i] = split[i].substr(0, 1).toUpperCase()   split[i].substr(1); // overwriting existing elements with Titlecased words

    return split.join('');  // returning final string

}

console.log(generateHashtag('Hello my name is'))

CodePudding user response：

You don't need to use join at all, just declare and initialize finalResult outside the loop and concatenate each word inside the loop:

function generateHashtag(str) {

    const split = str.split(' '); // Array<String>
    let finalResult = ''; // String

    for(let i = 0; i < split.length; i  ) {

        const titleCased = split[i].charAt(0).toUpperCase()   split[i].substring(1);
        finalResult  = titleCased;
    }

    return finalResult;
}

console.log(generateHashtag('Hello my name is'));

However, you can simplify this code considerably by using a functional-programming (FP) style with map and reduce. See below.
I've also changed your code to use toLocaleUpperCase instead of toUpperCase and uses [0] for brevity.
It's still safe to use substring(1) for single-character strings, it just returns ''.

function generateHashtag(str) {
    return ( str
        .split(' ')
        .map( word => word[0].toLocaleUpperCase()   word.substring(1).toLocaleLowerCase() )
        .reduce( ( word, concat ) => concat   word, "" )
    );
}

I forgot that join() can still be used instead of reduce (and will have an optimized implementation inside the JS engine anyway):
I've also moved the map function's logic to a named function toTitleCase.

function generateHashtag(str) {
    
    const toTitleCase( word ) => word[0].toLocaleUpperCase()   word.substring(1).toLocaleLowerCase();

    return ( str
        .split(' ')
        .map( word => toTitleCase( word ) ) // or just `.map( toTitleCase )`
        .join()
    );
}

The return statement has parens to prevent unwanted automatic-semicolon-insertion which would otherwise break the function.

CodePudding user response：

//try this code solve your problem 

const generateHashtag = str => {
    let split = str.split(' ')
    let finalResult = []
    for (word of split) {
        finalResult.push(word[0].toUpperCase()   word.substring(1))
    }
    return finalResult.join('')
}

console.log(generateHashtag('Hello my name is'))

CodePudding user response：

If you want something similar to your code, but working, i would do this:

function generateHashtag (str) {
  let split = str.split(' ')
  let newStr = []

  for (let i = 0; i < split.length; i  ){
    newStr.push(split[i].charAt(0).toUpperCase()   split[i].substring(1))
  }

  return newStr.join('')
}

You could also choose to do this task using a 'regular expression'. https://cheatography.com/davechild/cheat-sheets/regular-expressions/

Here is a quick implementation:

const generateHashtag = str => {
  // regular expression to capitalize the words
  const regEx = /(\b[a-z](?!\s))/g
  str = str.replace(regEx, (char) => {
    return char.toUpperCase()
  });

  // remove spaces, return
  return str.split(' ').join('')
}

Same code, but with less readability:

const generateHashtag = str => {
  return str.replace(/(\b[a-z](?!\s))/g, (char) => {
    return char.toUpperCase()
  }).split(' ').join('');
}

CodePudding user response：

function generateHashtag (str) {
    return str.replace(/\b\S/g, e => e.toUpperCase()).replace(/\s/g,'');
}

console.log(generateHashtag('Hello my name is'))

\b: bondary \S: non space \s: space. https://regex101.com/