Is There A Beforesend Javascript Promise?

I am using a script to send data to google drive. The script has two functions to detect when the request was sent or not. Is there a function alternative to jquery beforesend? To

Solution 1:

No there's not, but you can wrap it in your own function that you use everywhere.

functionmyFetch() {
    console.log('about to send');
    return fetch.apply(this, arguments);
}

 myFetch('/echo').then(e =>console.log(e));

Solution 2:

There is no native way to have hooks on calls to window.fetch. You could create a minimal wrapper class that executes that call for you, and allow you to pass before-send hooks to it that it will execute in advance:

//-----------------------------------------------------------// Implementation://-----------------------------------------------------------classCustomFetch {

    constructor(url, init = {}) {
        this.url = url;
        this.init = init;
        this.promise = null;
        this.beforeSends = [];
    }

    /**
     * Runs the actual fetch call.
     * @return {Promise<Response>}
     */fetch() {
        this._runBeforeSends();
        this.promise = fetch(this.url, this.init);
        returnthis.promise;
    }

    /**
     * Runs all registered before-send functions
     */_runBeforeSends() {
        this.beforeSends.forEach(fn =>fn(this));
        returnthis;
    }

    /**
     * Register a beforesend handler.
     * @param {function(url, init): void} fn
     */beforeSend(fn) {
        this.beforeSends.push(fn);
        returnthis;
    }
}

//-----------------------------------------------------------// Usage example://-----------------------------------------------------------// Create a special fetch wrapper with pre-defined arguments for 'Actual fetch':const postFetch = newCustomFetch('https://jsonplaceholder.typicode.com/posts/1');

// Register a before-send handler:
postFetch.beforeSend((fetch) => {
  console.log(`About to send to ${fetch.url}`);
});
  

// call the fetch() method and get back the Promise<Response>// of the native fetch call:const posP = postFetch.fetch();

// When loaded, log the response data
posP.then((res) => res.json()).then(console.log);

This is a little more verbose than a simple function wrapper, but also gives you the advantage of being able to re-use a CustomFetch instance – you can keep calling someFetch.fetch(), and it will in turn keep calling the registered before-send handlers before proceeding with calling window.fetch.