字符串中的第一个字母增加，最后一个字母减少

Question

I'm trying to create a simple encoder, where the first letter of every word becomes it's successor (A = B) and the last letter becomes its predecessor (B = A).

Like so:

 KEY: The first letter goes up, the last letter goes backwards. </p> If it is the first letter in the string, <span style='color: red;'>x</span> should be converted to <span style='color: blue;'>y</span>, as seen below: </p> <span style='color: red;'>Aa</span> = <span style='color: blue;'>Bb</span> </p> <span style='color: red;'>Bb</span> = <span style='color: blue;'>Cc</span> </p> <span style='color: red;'>Cc</span> = <span style='color: blue;'>Dd</span> </p> <span style='color: red;'>Dd</span> = <span style='color: blue;'>Ee</span> </p> and so on.... </p> If it is the last letter in the string, <span style='color: lightgreen;'>x</span> should be converted to <span style='color: orange;'>y</span>, as seen below: </p> <span style='color: lightgreen;'>Aa</span> = <span style='color: orange;'>Zz</span> </p> <span style='color: lightgreen;'>Bb</span> = <span style='color: orange;'>Aa</span> </p> <span style='color: lightgreen;'>Cc</span> = <span style='color: orange;'>Bb</span> </p> <span style='color: lightgreen;'>Dd</span> = <span style='color: orange;'>Cc</span> </p> and so on.... </p> <div class="encode"> The fox jumped over the dog. = Uhd gow kumpec pveq uhd eoh. </div> 

I'm trying to accomplish this using javaScript, however, I am open to using any language that will make this possible.

This code is the gist of what I'm looking for, but I need to target the first and last letter of every word in a div:

var strRandomString = "I have 2 apples and 6 oranges and 3 grapes";
strRandomString.replace(/apples|oranges/g, function(m) {
    // `m` is a matched string.
    return m === 'apples' ? 'oranges' : 'apples';
})
// => "I have 2 oranges and 6 apples and 3 grapes"

Unfortunately, I do not have any actual sample javaScript code (but the above code can count as an attempt, a failed one), as I've been researching for about half an hour and couldn't find a viable solution.

I've scoured the following threads for help:

https://codereview.stackexchange.com/questions/32620/replacing-every-letter-in-a-string-with-the-letter-following-it-in-the-alphabet

Promoting letters in a string to previous letter in java

https://coderanch.com/t/552363/java/Replacing-characters-string

http://www.dreamincode.net/forums/topic/326746-question-shifting-characters-to-the-next-letter-in-the-alphabet/

https://www.extendoffice.com/documents/excel/4027-excel-increase-letter-by-one.html (yep, I was so desperate that I was about to use excel).

Answer 1

This works for a word, but also a phrase

function transform(phrase)
{ var i,last,letters,words=phrase.split(/\s+/);
  for(i=0;i<words.length;i++)
  { letters=words[i].split('');
    last=letters.length-1;
    letters[0]=letters[0].charCodeAt(0)<122?String.fromCharCode(letters[0].charCodeAt(0)+1):'a';
    letters[last]=97<letters[last].charCodeAt(0)?String.fromCharCode(letters[last].charCodeAt(0)-1):'z';
    words[i]=letters.join('');
  }
  return words.join(' ');
}

console.log(transform('apple zebra variables'));
//outputs 'bppld aebrz wariabler'

Answer 2

To make it obvious, I simply created some functions then call them.

Issues with this, single letter words like "a" get double messed with so "a" becomes "z" then back to "a" as the first and last letter.

 // I used this to remove the empty "" from the array, there might be better ways that altering the prototype but that might be opinion. Array.prototype.clean = function(deleteValue) { for (var i = 0; i < this.length; i++) { if (this[i] == deleteValue) { this.splice(i, 1); i--; } } return this; }; // wrap to begin using same case function prevLetter(letter) { if (letter === 'a') { return 'z'; } if (letter === 'A') { return 'Z'; } return String.fromCharCode(letter.charCodeAt(0) - 1); } // wrap to end using same case function nextLetter(letter) { if (letter === 'z') { return 'a'; } if (letter === 'Z') { return 'A'; } return String.fromCharCode(letter.charCodeAt(0) + 1); } // last letter of word function getLastLetter(myword) { return myword.slice(-1); } // first letter of word function getFirstLetter(myword) { return myword.charAt(0); } //split sentence into array by the ;,. and space function splitString(mystring) { return mystring.split(/[ ;,.]+/); } // replace a character (first,last) function setCharAt(mystring, index, chr) { if (index > mystring.length - 1) return mystring; return mystring.substr(0, index) + chr + mystring.substr(index + 1); } var mySentence = "The big, brown; cow ran over a zebra. I get this"; // words in the sentence to mess with var splitS = splitString(mySentence).clean(""); for (var i = 0; i < splitS.length; i++) { var newS = setCharAt(splitS[i], 0, nextLetter(getFirstLetter(splitS[i]))); var newSE = setCharAt(newS, newS.length - 1, prevLetter(getLastLetter(newS))); splitS[i] = newSE; } // the words in the array now are messed with console.log(splitS);