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javascriptecmascript-6es6-promise

Avoid a promise to execute when created

I do not want a promise to run before it is actually called by the script, but unfortunately a promise by default runs the moment it's created.

Is there a way to avoid this default execution of the code when the promise is created?

Solution

  • You can put it in a function that returns the promise, then call the promise later.

    Set up your function which returns a promise:

    function myAsyncFunction(url) {
  return new Promise((resolve, reject) => {
    const xhr = new XMLHttpRequest();
    xhr.open("GET", url);
    xhr.onload = () => resolve(xhr.reponse);
    xhr.onerror = () => reject(xhr.statusText);
    xhr.send();
    //  Or whatever you want in your function
  });
}

    Then later, call your function:

     myAsyncFunction(url)
   .then( ... ) 
   .then( ... ) 
   .catch( ... )