javascript
Promise Chaining
new Promise(function (resolve, reject) {
setTimeout(() => resolve(1), 1000); // (*)
}).then(function (result) { // (**)
alert(result); // 1
return result * 2;
}).then(function (result) { // (***)
alert(result); // 2
return result * 2;
}).then(function (result) {
alert(result); // 4
return result * 2;
});The idea is that the result is passed through the chain of .then handlers.
Here the flow is:
1. The initial promise resolves in 1 second (*) ,
2. Then the .then handler is called (**) .
3. The value that it returns is passed to the next .then handler (***)
4. …and so on.
As the result is passed along the chain of handlers, we can see a sequence of alert calls: 1
→ 2 → 4 .
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