What is a promise
A promise represents the eventual result of an asynchronous operation A promise is an object that is used as a placeholder for the eventual result of a deferred and possibly asynchronous computation. A promise can be created as
var myPromise = new Promise(function(resolve,reject){
});
From above, it is obvious that promise takes a function with two parameters
- resolve
- reject
resolve is a function that should be called when the Promise needs to return the value.
reject is a function that should be called when there is an error condition.
Following is a pseudo code of what a typical promise call will look like
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| var promiseRemoteData = new Promise(function(resolve,reject){ | |
| // 1. Perform ASYNC operation | |
| // 2. On completion of remote operation call | |
| // – resolve to notify success (pass any values that is required) | |
| // – reject to notify error condition | |
| } |