Reusing Requests

Reusing Request ObJects

Requests with Bodies(POST, PUT)

If a Request object is used more than once in a Fetch request that involves bodies (POST, PUT) it will throw an error.

Notice how an error is thrown if a Request object is fetched again after being previously used in a POST request:

let initObject = {
    method: 'POST',
    headers: new Headers(),
    mode: 'cors',
    body: "{}" 
}

var request = new Request("https://jsonplaceholder.typicode.com/posts",initObject)

//first time using Request object
fetch(request).then(function(result){  
    return result.json() 
}).then(function(result){
    console.log(result); //logs Object {id: 101}
}).catch(function(err){
    console.log(err);
});



//second time using Request object
fetch(request).then(result => {
    return result.json();
}).catch(err => {
    console.log(err.message) // logs "Failed to execute 'fetch' on 'Window': Cannot construct a Request with a Request object that has already been used."
});

Requests without Bodies (GET, HEAD)

However, Request objects can be used more than once in Fetch requests that don't involve bodies(Head, Get).

Notice how a Request object can be reused in multiple GET requests:

//makes a GET request
var request = new Request("https://jsonplaceholder.typicode.com/todos/1")

//first fetch request
fetch(request).then(result => { 
   console.log(result.status) //logs 200, OK fetch response
})

//reusing request object 
fetch(request).then(result => { 
   console.log(result.status) //logs 200, OK fetch response after reusing request object
});