Intercept Fetch() API responses and request in Javascript

Question

I want to intercept the fetch API request and response in Javascript.

For ex: Before sending the request want to intercept the request URL and once get the respons

Answer 1

For intercepting the response body you need to create a new Promisse and resolve or reject current into "then" code. It solved for me and keep content for real app . eg. react etc..

const constantMock = window.fetch;
 window.fetch = function() {
  console.log(arguments);

    return new Promise((resolve, reject) => {
        constantMock.apply(this, arguments)
            .then((response) => {
                if(response.url.indexOf("/me") > -1 && response.type != "cors"){
                    console.log(response);
                    // do something for specificconditions
                }
                resolve(response);
            })
            .catch((error) => {
                reject(response);
            })
    });
 }