ES6 Promise

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Promise

Promise, like Generator from the previous chapter, is also a solution for asynchronous programming.

You can find similar approaches for handling async operations in jQuery and Angular.

Basic Usage


// First, instantiate a Promise
var promise = new Promise(function(resolve, reject) {
  // Promise has two parameters: resolve and reject — one for success, one for failure

  if (/* true or false */){
    resolve(value); // Success: executes the first callback of promise.then
  } else {
    reject(error); // Failure: executes the second callback of promise.then
  }

});


promise.then(function(value){

  // When resolve() runs in the Promise function, this executes
  // It receives the parameter passed to resolve

},function(error){

  // When reject() runs in the Promise function, this executes
  // It receives the parameter passed to reject

}).catch(function(error){

  // If either callback in then throws an error, catch handles it
  // This prevents the code from stopping execution due to errors

})

That’s a complete Promise usage example. Simple, isn’t it?

Article Link:

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