javascript fetch - Failed to execute 'json' on 'Response': body stream is locked

Question

When the request status is greater than 400(I have tried 400, 423, 429 states), fetch cannot read the returned json content. The following error is displayed in the browser cons

Answer 1

As mentioned in the question when you're trying to use same response object, your body is about to locked due to state of the object. What you can do is that capture the value of the response object and then try to have some operation on it (.then()). Please follow the code below,

fetch('someurl').then(respose) => {
    let somedata = response.json(); // as you will capture the json response, body will not be locked anymore. 
    somedata.then(data) => {
        {
             error handling (if (data.err) { ---- })
        }
        {
             operations (else { ---- })
        }
    } 
}