Javascript – Remove not alphanumeric characters from string

javascriptregex

I want to convert the following string to the provided output.

Input:  "\\test\red\bob\fred\new"
Output: "testredbobfrednew"

I've not found any solution that will handle special characters like \r, \n, \b, etc.

Basically I just want to get rid of anything that is not alphanumeric. Here is what I've tried…

Attempt 1: "\\test\red\bob\fred\new".replace(/[_\W]+/g, "");
Output 1:  "testedobredew"

Attempt 2: "\\test\red\bob\fred\new".replace(/['`~!@#$%^&*()_|+-=?;:'",.<>\{\}\[\]\\\/]/gi, "");
Output 2:  "testedobred [newline] ew"

Attempt 3: "\\test\red\bob\fred\new".replace(/[^a-zA-Z0-9]/, "");
Output 3:  "testedobred [newline] ew"

Attempt 4: "\\test\red\bob\fred\new".replace(/[^a-z0-9\s]/gi, '');
Output 4:  "testedobred [newline] ew"

One other attempt with multiple steps

function cleanID(id) {
    id = id.toUpperCase();
    id = id.replace( /\t/ , "T");
    id = id.replace( /\n/ , "N");
    id = id.replace( /\r/ , "R");
    id = id.replace( /\b/ , "B");
    id = id.replace( /\f/ , "F");
    return id.replace( /[^a-zA-Z0-9]/ , "");
}

with results

Attempt 1: cleanID("\\test\red\bob\fred\new");
Output 1: "BTESTREDOBFREDNEW"

Any help would be appreciated.

Working Solution:

Final Attempt 1: return JSON.stringify("\\test\red\bob\fred\new").replace( /\W/g , '');
Output 1: "testredbobfrednew"

Best Answer

Removing non-alphanumeric chars

The following is the/a correct regex to strip non-alphanumeric chars from an input string:

input.replace(/\W/g, '')

Note that \W is the equivalent of [^0-9a-zA-Z_] - it includes the underscore character. To also remove underscores use e.g.:

input.replace(/[^0-9a-z]/gi, '')

The input is malformed

Since the test string contains various escaped chars, which are not alphanumeric, it will remove them.

A backslash in the string needs escaping if it's to be taken literally:

"\\test\\red\\bob\\fred\\new".replace(/\W/g, '')
"testredbobfrednew" // output

Handling malformed strings

If you're not able to escape the input string correctly (why not?), or it's coming from some kind of untrusted/misconfigured source - you can do something like this:

JSON.stringify("\\test\red\bob\fred\new").replace(/\W/g, '')
"testredbobfrednew" // output

Note that the json representation of a string includes the quotes:

JSON.stringify("\\test\red\bob\fred\new")
""\\test\red\bob\fred\new""

But they are also removed by the replacement regex.

Related Solutions

Javascript – Remove properties from objects (JavaScript)

To remove a property from an object (mutating the object), you can do it like this:

delete myObject.regex;
// or,
delete myObject['regex'];
// or,
var prop = "regex";
delete myObject[prop];

Demo

var myObject = {
    "ircEvent": "PRIVMSG",
    "method": "newURI",
    "regex": "^http://.*"
};
delete myObject.regex;

console.log(myObject);

For anyone interested in reading more about it, Stack Overflow user kangax has written an incredibly in-depth blog post about the delete statement on their blog, Understanding delete. It is highly recommended.

If you'd like a new object with all the keys of the original except some, you could use the destructuring.

Demo

let myObject = {
  "ircEvent": "PRIVMSG",
  "method": "newURI",
  "regex": "^http://.*"
};

const {regex, ...newObj} = myObject;

console.log(newObj);   // has no 'regex' key
console.log(myObject); // remains unchanged

Javascript – How to convert a string to boolean in JavaScript

Do:

var isTrueSet = (myValue === 'true');

using the identity operator (===), which doesn't make any implicit type conversions when the compared variables have different types.

Don't:

You should probably be cautious about using these two methods for your specific needs:

var myBool = Boolean("false");  // == true

var myBool = !!"false";  // == true

Any string which isn't the empty string will evaluate to true by using them. Although they're the cleanest methods I can think of concerning to boolean conversion, I think they're not what you're looking for.