The following code works as a Caesar’s Cipher, however, I cannot figure out why if I make the regex global (/[A-Z]/g) it produces strange results. Where it gets even more strange is if I uncomment the .match() method in the middle, the cipher works again even though the global regex remains… if I uncomment the the .test() method in the middle I get even different results.
function rot13(str) {
console.log(str);
let reg = /[A-Z]/
let alpha = 'ABCDEFGHIJKLMNOPQRSTUVWXYZABCDEFGHIJKLMNOPQRSTUVWXYZ';
let alphaArr = alpha.split('');
let newStr = ''
for (let i = 0; i < str.length; i++) {
//console.log(str[i].match(reg))
//console.log(reg.test(str[i]));
if (reg.test(str[i])) {
newStr += alphaArr[alphaArr.indexOf(str[i]) + 13]
} else {
newStr += str[i];
}
}
return newStr;
}
console.log(rot13("SERR PBQR PNZC"));
I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.
You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.
Can you be more specific by what you mean by “strange”? What may seem strange to you may seem normal to someone that uses regex.
If I look in the docs (a habit every dev should nurture), I read that:
JavaScript RegExp objects are stateful when they have the global or sticky flags set (e.g. /foo/g or /foo/y). They store a lastIndex from the previous match. Using this internally, test() can be used to iterate over multiple matches in a string of text (with capture groups).
In other words, with the g flag, it’s not starting new search each time but is continuing with the old one.
