Creating a (ES6) promise without starting to resolve it

Question

Using ES6 promises, how do I create a promise without defining the logic for resolving it? Here\'s a basic example (some TypeScript):

Answer 1

Good question!

The resolver passed to the promise constructor intentionally runs synchronous in order to support this use case:

var deferreds = [];
var p = new Promise(function(resolve, reject){
    deferreds.push({resolve: resolve, reject: reject});
});

Then, at some later point in time:

 deferreds[0].resolve("Hello"); // resolve the promise with "Hello"

The reason the promise constructor is given is that:

• Typically (but not always) resolution logic is bound to the creation.
• The promise constructor is throw safe and converts exceptions to rejections.

Sometimes it doesn't fit and for that it the resolver runs synchronously. Here is related reading on the topic.