CODEWITHSUNDEEP
javascriptescaping
Explosion
Explosion

Reputation: 326

How do I unescape backslash escaped characters?

How can I unescape a string like this in JavaScript

alert(\"Testing\");\nconsole.log(\"Hello\");

so that is is escaped to this:

alert("Testing");
console.log("Hello");

I have a program which uses an api and returns the escaped string, but I want to replace the escaped version of the string with the literal representation, e.g. "\n" with a newline. I saw a question, which had this code to escape a string, but it did not say how to undo the operation, to better understand how the string is escaped here is the function in question which escapes a string:

function addslashes(string) {
    return string.replace(/\\/g, '\\\\').
        replace(/\u0008/g, '\\b').
        replace(/\t/g, '\\t').
        replace(/\n/g, '\\n').
        replace(/\f/g, '\\f').
        replace(/\r/g, '\\r').
        replace(/'/g, '\\\'').
        replace(/"/g, '\\"');
}

I pretty much want to undo that. Thanks in advance!

Edit

Turns out I can do something like this:

var string = "<!DOCTYPE html><script>alert(\"Hello\");<\/html>"
console.log(unescape(escape(string)));

Upvotes: -1

Views: 1367

Answers (2)

Mark
Mark

Reputation: 6306

As this is the first hit on Google for unescaping backslashed characters in JavaScript, here's a function that should undo JavaScript's literal escaping:

const unescapeBackslashes = s => s.replaceAll("\\'", "\'").replaceAll('\\"', '\"').replaceAll('\\n', '\n').replaceAll('\\r', '\r')
                                  .replaceAll('\\t', '\t').replaceAll('\\b', '\b').replaceAll('\\f', '\f').replaceAll('\\v', '\v')
                                  .replace(/\\x([0-9A-Fa-f]{2})/g, (match, code) => String.fromCharCode(parseInt(code, 16)))
                                  .replace(/\\[0-3]([0-7]{1,2})/g, (match, code) => String.fromCharCode(parseInt(code, 8)))
                                  .replaceAll('\\', '');

E.g.

> str = 'alert(\\"Testing\\");\\nconsole.log(\\"Hello\\");'
> console.log(unescapeBackslashes(str))
alert("Testing");
console.log("Hello");

Upvotes: -1

FoundingBox
FoundingBox

Reputation: 613

There's a built in unescape() function you can use

const unescaped = unescape(`alert(\"Testing\");\nconsole.log(\"Hello\");`);
console.log(unescaped)

Here's an alternative answer that undoes the specific encoding you did 

const escapedString = `alert(\"Testing\");\nconsole.log(\"Hello\");`

function removeSlashes(string) {
    return string.replace('\\\\', /\\/g).
        replace('\\b', /\u0008/g).
        replace('\\t', /\t/g).
        replace('\\n', /\n/g).
        replace('\\f', /\f/g).
        replace('\\r', /\r/g).
        replace('\\\'', /'/g).
        replace('\\"', /"/g);
}

console.log(removeSlashes(escapedString));

Upvotes: -1

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