Example usage of Promise exception capture in javascript

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1. In the then method of promise, we have automatically helped us with the try catch callback function.

Promise.prototype.then = function (cb) {try {cb ()} catch (e) {/ / todo reject (e)}}

2. The exception thrown in the then method will be caught by the second parameter of the next cascading then method.

Promise.prototype.done = function (resolve, reject) {this.then (resolve, reject) .catch (function (reason) {setTimeout (() = > {throw reason;}, 0);});}

If the last then has an exception, you can add a done method, which does not return a promise object, so it cannot be cascaded later. The done method eventually throws the exception globally so that the thread can be caught or interrupted by the global exception handler. This is also the best practice strategy for promise.

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