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Capitalize First Letter - JavaScript Algorithms

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    Curtis Warcup

Directions: Write a function that accepts a string. The function should capitalize the first letter of each word in the string then return the capitalized string.


capitalize('a short sentence') --> 'A Short Sentence'
capitalize('a lazy fox') --> 'A Lazy Fox'
capitalize('look, it is working!') --> 'Look, It Is Working!'

Solution 1: slice()

We can use the built in javascript method slice(startIndex, endIndex) and concatenate the first letter to the rest of the string.

  1. Make an empty array to contain the capitalized words.
  2. Use split() on the input string to split the string into an array of words, splitting on spaces.
  3. For each word in the array...
    • Use toUpperCase() on the first letter of the word.
    • Join first letter with rest of the string
    • Push results into the empty array.
  4. Join the array containing the capitalized words into a string and return the result.
function capitalize(str) {
  let words = []
  for (let word of str.split(' ')) {
    words.push(word[0].toUpperCase() + word.slice(1))

  return words.join(' ')

Solution 2: For...of Loop

  1. Initialize a string with the capitalized version of the first letter of the input string.
  2. For each character in the string...
    • IF the character to the left is a space
      • use toUpperCase() on the character
      • push it into the string containing the capitalized words.
    • ELSE
      • push the character into the string containing the capitalized words.
  3. Return the newly created string.
function capitalize(str) {
  let result = str[0].toUpperCase()

  for (let i = 1; i < str.length; i++) {
    if (str[i - 1] === ' ') {
      result += str[i].toUpperCase()
    } else {
      result += str[i]
  return result