wrap-promise
v1.0.1
Published
Like new Promise(), but prevents implicit rejection
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25,357
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wrap-promise
Like new Promise()
, but prevents implicit rejection
Comparison
Using the native new Promise()
const fs = require('fs');
new Promise((resolve, reject) => {
// Node's fs.readFile throws a type error when the first argument is not a string.
fs.readFile(123, (err, buf) => { // doesn't throw, but calls `onRejected` function
if (err) {
reject(err);
return;
}
resolve(buf);
});
}).catch(() => console.log('This function should be called.'));
Using wrap-promise
const fs = require('fs');
const wrapPromise = require('wrap-promise');
wrapPromise((resolve, reject) => {
fs.readFile(123, (err, buf) => { // doesn't call `onRejected` but throws immediately
if (err) {
reject(err);
return;
}
resolve(buf);
});
}).catch(() => console.log('This function should not be called.'));
According to the Promise specification, a promise
will be rejected implicitly when an error is thrown in the constructor callback. The only (and the biggest) difference is that wrap-promise immediately throws an error in such a case.
Installation
Package managers
npm
npm install wrap-promise
Bower
bower install wrap-promise
Duo
const wrapPromise = require('shinnn/wrap-promise');
Standalone
Download the script file directly.
API
wrapPromise(fn)
fn: Function
Return: Object
(Promise)
It can be used in the same way as new Promise()
but new
operator is not needed.
wrapPromise.Promise
Type: Function
Default: global Promise
or require('es6-promise').Promise
The Promise
constructor used in wrapPromise
function.
On CommonJS-based environment (e.g. Node)
By default it uses the global Promise
constructor if available, otherwise it require
s es6-promise and use its Promise
property.
If you don't need the fallback, use no-fallback.js
instead. (Useful for Browserify)
const wrapPromise = require('wrap-promise/no-fallback');
On non-CommonJS environment
It uses the global Promise
constructor without any fallbacks. Before using wrapPromise
, you must load Promise
polyfill if Promise
doesn't exist by default.
License
Copyright (c) 2014 - 2015 Shinnosuke Watanabe
Licensed under the MIT License.