How to use string.replace() with JSON strings?

Question

I have a backend that's sending invalid JSON strings. It escapes vertical tabs as \v which is not valid in JSON and ends up being rejected by the parser.

I am trying to remedy the problem in the frontend JSON decoder:

function fromJson(json) {
  if(typeof json === "string") {
    var jsonString = json.replace(/\v/g, "\u000B");
    return JSON.parse(jsonString)
  }
  else {
    return json
  }
}

Expected output: new string with all instances of \v replaced with the unicode line tabulation.

Actual output:

JSON.parse: SyntaxError: Unexpected token v in JSON at position...

Kindly post your JSON input. It seems String replace method is affecting the structure of your JSON. — Nirjhar Bera
– Nirjhar Bera, Commented Mar 29, 2019 at 12:39

D Malan · Accepted Answer · 2019-03-29 12:40:58Z

1

Javascript interprets \ characters as special characters in regular expressions. It expects the character after the \ to have a special meaning, but v isn't one of the special characters. Hence the exception Unexpected token v in JSON.

To fix your issue you need to escape the \ character in your regex with another \, e.g. json.replace(/\\v/g, "\u000B");

answered Mar 29, 2019 at 12:40

D Malan

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1 Comment

Miggoh Over a year ago

Thank you, this did the trick after also correctly escaping the unicode escape character.

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