Was working with javascript promises in a project and at one point I needed to know how .then worked with having a promise inside of it.
Here is what I found promises have to resolve before the .then will fire. If you want to have a promise inside a then you can do that but it needs to be a resolved promise. Here is some example code.
new Promise(function(resolve, reject) {
setTimeout(() => resolve(1), 1000);
}).then(function(result) {
alert(result); // 1
return new Promise((resolve, reject) => { // (*)
setTimeout(() => resolve(result * 2), 1000);
});
}).then(function(result) { // (**)
alert(result); // 2
return new Promise((resolve, reject) => {
setTimeout(() => resolve(result * 2), 1000);
});
}).then(function(result) {
alert(result); // 4
});
Also here is some documentation on promises from javascript.info https://javascript.info/promise-chaining
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