longest-prefix.js

/**
 * Write a function to find the longest common prefix string in an array of strings.
 * --------------------------------
 * Function to find matching characters and stop at the 
 * point at which they are different or if the string ends
 * 
 * Worked with https://twitter.com/Spraggsz_ to solve!
 * @return {string}
 */

function longestPrefix (arrayOfStrings) {
  let string = ''
  let shortestStringLength = null 

  for (const array of arrayOfStrings) {
    const isSmaller = shortestStringLength === null || shortestStringLength > array.length
    if (isSmaller) {
      shortestStringLength = array.length
    }
  }

  for (let i = 0; i < shortestStringLength; i++) {
    // compare all arrayOfStrings[i] to see if they are equal
    const firstChar = arrayOfStrings[0][i]
    for (let j = 1; j < arrayOfStrings.length; j++) {
      if (firstChar !== arrayOfStrings[j][i]) {
        return string
      }
    }
    string += firstChar
  }

  return string
}


longestPrefix([
  "parrot", 
  "poodle", 
  "fish"
])
// ''

longestPrefix([
  "cranberries", 
  "crawfish", 
  "crap" 
])

// 'cra'