Error in Fetch Response: Invalid escape character encountered in JSON data

Question

Error in Fetch Response: Invalid escape character encountered in JSON data

I'm currently facing an issue with a fetch request that communicates with an API and receives a JSON object in return. The problem arises when the API includes escape characters for single quotes, such as isn\'t. This causes an error during the JSON parsing process, leading me to seek a way to manipulate the response body before calling response.json(). Below is the snippet of my existing code:

    httpCallout(){
    fetch('/1.0/?method=getQuote&lang=en&format=json', {method: "GET", cache: "no-cache"})
    .then(response => {
      return response.json()
    })
    .then((data) => {
      const quote = data.quoteText;
      this.setState({
        quote: quote,
        author: data.quoteAuthor
      });
    });
    this.colorChange(rgb);
  }

The main issue occurs specifically when response.json encounters an escaped single quote. While I could simply catch the error and move on, I am determined to find a solution that allows me to remove the escaped single quote and still update my state accordingly.

In essence, my goal is to alter a response containing a quoteText value like

"It\'s tiring isn\'t it?"

to be properly parsed as

"It's tiring isn't it?"

before executing response.json() to prevent any Bad escape character errors.

javascript json http fetch

Answer 1

Answer №1

If you're struggling to convince the data provider to tidy up their database or JSON encoding process, there is still a way to clean up the text manually:

convert the Response to text using Body.text() (instead of Body.json())
replace the problematic section with String.replaceAll()
explicitly parse the JSON with JSON.parse()

Combining these steps in your function will look something like this:

function httpCallout () {
  fetch('/1.0/?method=getQuote&lang=en&format=json', { method: 'GET', cache: 'no-cache' })
    .then(response => response.text())
    .then(text => {
      const cleanText = text.replaceAll("\\'", "'");
      return JSON.parse(cleanText);
    })
    .then(data => {
      const quote = data.quoteText;
      this.setState({
        quote: quote,
        author: data.quoteAuthor
      });
    });
  this.colorChange(rgb);
}

When specifying the arguments for String.replaceAll(), remember to double escape the initial backslash but leave the single quote untouched, resulting in:

text.replaceAll("\\'", "'")

Answer 2

If you're struggling to convince the data provider to tidy up their database or JSON encoding process, there is still a way to clean up the text manually:

convert the Response to text using Body.text() (instead of Body.json())
replace the problematic section with String.replaceAll()
explicitly parse the JSON with JSON.parse()

Combining these steps in your function will look something like this:

function httpCallout () {
  fetch('/1.0/?method=getQuote&lang=en&format=json', { method: 'GET', cache: 'no-cache' })
    .then(response => response.text())
    .then(text => {
      const cleanText = text.replaceAll("\\'", "'");
      return JSON.parse(cleanText);
    })
    .then(data => {
      const quote = data.quoteText;
      this.setState({
        quote: quote,
        author: data.quoteAuthor
      });
    });
  this.colorChange(rgb);
}

When specifying the arguments for String.replaceAll(), remember to double escape the initial backslash but leave the single quote untouched, resulting in:

text.replaceAll("\\'", "'")

Error in Fetch Response: Invalid escape character encountered in JSON data

Answer №1

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