How to catch 401 error using fetch method of javascript

Question

I need to catch error 401 Code of response so that I can retry after getting a new token from token endpoint. I am using fetch method get data from API.

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Answer 1

(function () {
var originalFetch = fetch;
fetch = function() {
    return originalFetch.apply(this, arguments).then(function(data) {
        someFunctionToDoSomething();
        return data;
    });
};})();

source Can one use the Fetch API as a Request Interceptor?