How do I replace substrings in my string with array objects?

Question

I am trying to replace special characters in a string, with the string being file names as special characters cannot be stored on the Windows filesystem.

What I have tried is simply using replace() on my variable repeatedly until it covers all of the special characters I want to replace. Example code:

//Formats file name to save to Filesystem
function formatFileName(postTitle, postUrl, nsfw) {
return new Promise(resolve => {
    //Filter out bad characters
    postTitle = postTitle.replace(/\?/g, "[q]");
    postTitle = postTitle.replace(/\//g, "[s]");
    postTitle = postTitle.replace(/\</g, "[l]");
    postTitle = postTitle.replace(/\>/g, "[m]");
    postTitle = postTitle.replace(/\"/g, "[quo]");
    postTitle = postTitle.replace(/\*/g, "[st]");

While this works, I know that there is definitely a better way out there to do this, and as such, I'd like to find out how I could do so in a cleaner manner.

I've tried refining the code by doing this instead:

    let specialCharacters = ["?", "/", "<", ">", "\"", "*", "\\"];
    let replacement = ["[q]", "[s]", "[l]", "[m]", "[quo]", "[st]", "[bs]"];

    //Replace special characters into filesystem-compatible ones
    for (var i = 0; i < specialCharacters.length; i++) {
        postTitle.replace(specialCharacters[i], replacement[i]);
    }

However, with the newly modified code, it does not replace any of the special characters in the string. I've also tried doing

    let specialCharacters = [/\?/g, /\//g, /\</g, /\>/g, /\"/g, /\*/g, /\\/g];
    let replacement = ["[q]", "[s]", "[l]", "[m]", "[quo]", "[st]", "[bs]"];

    //Replace special characters into filesystem-compatible ones
    for (var i = 0; i < specialCharacters.length; i++) {
        postTitle.replace(specialCharacters[i], replacement[i]);
    }
    console.log(postTitle);
    resolve(postTitle);

but the outcome did not change. Another thing I tried was to wrap it in an async/await function as I thought that it may be because NodeJS wasn't waiting for the loop to finish, but that did not change anything either.

Could someone please tell me what I'm doing wrong?

Answer 1

Strings in JavaScript are immutable. You are not reassigning the returned value from replace .

let specialCharacters = [/\?/g, /\//g, /\</g, /\>/g, /\"/g, /\*/g, /\\/g];
let replacement = ["[q]", "[s]", "[l]", "[m]", "[quo]", "[st]", "[bs]"];

//Replace special characters into filesystem-compatible ones
for (var i = 0; i < specialCharacters.length; i++) {
  // Assign return value to postTitle
  postTitle = postTitle.replace(specialCharacters[i], replacement[i]);
}
console.log(postTitle);

Answer 2

You can try this way:

 var specialCharacters = ['?', '/', '<', '>', '"', '*', '\\\\']; var replacement = ["[q]", "[s]", "[l]", "[m]", "[quo]", "[st]", "[bs]"]; var pattern = new RegExp(specialCharacters.map(x => '(\\\\' + x + ')').join('|'), 'g'); var str = "<span>What is your question?</span>"; console.log(str.replace(pattern, x => replacement[specialCharacters.indexOf(x)]));