Differences Between JSON.parse() and .json()There are distinct variations between

Recently, I've been diving into using fetch API and Promises, which led me to .json(). It's interesting how often .json() gives the same result as JSON.parse. After some initial confusion, I turned to Google for answers, only to be redirected in different directions.

Here is an example with XHR and JSON.parse:

$('#xhr').click(function(){
  var XHR = new XMLHttpRequest();

  XHR.onreadystatechange = function(){
    if (XHR.status == 200 && XHR.readyState == 4) {
      $('#quote').text(JSON.parse(XHR.responseText)[0]);
    }
  };

  XHR.open("GET", url);
  XHR.send();
});

And here is an example with Fetch API:

$('#fetch').click(function(){
  fetch(url)
  .then(function(res){
    return res.json();
  })
  .then(function(quote){
    $('#quote').text(quote);
  })
  .catch(function(err){
    handleError(err);
  });
});

I'm still confused though – can someone explain the distinction between these seemingly similar concepts? Thanks!

Answer №1

Body.json() operates asynchronously, delivering a Promise object that resolves to a JavaScript object. On the other hand, JSON.parse() functions synchronously by parsing a string and producing an altered JavaScript object upon completion.

Answer №2

Coding with 'AJAX' involves utilizing 'callbacks', while coding with 'fetch' involves utilizing 'promises'.

For parsing the response in AJAX, make use of JSON.parse(); for fetch, utilize json().

Answer №3

When using the json() method from the Body mixin, it takes a Response stream and reads it until completion. The method then returns a promise that resolves with the result obtained from parsing the body text as JSON. On the other hand, the JSON.parse() method is responsible for parsing a JSON string and creating the corresponding JavaScript value or object based on the provided string.

Remember to utilize JSON.parse() when dealing with AJAX response parsing, and use json() for handling response parsing in fetch requests.

Answer №4

I believe that both res.json and JSON.parse serve the same purpose. However, I personally prefer using res.json due to its syntax. To illustrate this point further, here is an example:

 this.api.getData() //calling API
.then((response) => {
 this.dataDetails = JSON.parse(response._data); //you can use this method
 this.dataDetails = response.json(); //or alternatively use this syntax
 )}
.catch()

Using either of these methods will give you access to the complete response body and help you understand their functionalities better.

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