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var Promise = require('bluebird'); | |
// EXAMPLE 1 | |
// EXAMPLE 1 | |
// EXAMPLE 1 | |
// ERROR HANDLER WILL CATCH REJECTION | |
function getPromise1(){ | |
return new Promise(function(resolve, reject){ | |
reject(new Error("Rejected error")) | |
}).then(function(result) { | |
console.log('Result 1 ' + result); | |
return result; | |
}).then(function(result) { | |
console.log('Result 2 ' + result) | |
return result; | |
}); | |
} | |
getPromise1() | |
.then(function(finalResult){console.log("Final result " + finalResult)}) | |
.error(function(e){console.log("Error handler " + e)}) | |
.catch(function(e){console.log("Catch handler " + e)}); | |
// EXAMPLE 2 | |
// EXAMPLE 2 | |
// EXAMPLE 2 | |
// CATCH HANDLER WILL CATCH REJECTION | |
function getPromise2(){ | |
return new Promise(function(resolve, reject){ | |
throw new Error("Throw error") | |
}).then(function(result) { | |
console.log('Result 1 ' + result); | |
return result; | |
}).then(function(result) { | |
console.log('Result 2 ' + result) | |
return result; | |
}); | |
} | |
getPromise2() | |
.then(function(finalResult){console.log("Final result " + finalResult)}) | |
.error(function(e){console.log("Error handler " + e)}) | |
.catch(function(e){console.log("Catch handler " + e)}); | |
// EXAMPLE 3 | |
// EXAMPLE 3 | |
// EXAMPLE 3 | |
// If you throw error instead of reject here outside the promise | |
// It will not be caught correctly unless you do a tradtional try/catch around the getPromise3() call | |
function getPromise3(someparameter){ | |
if (!someparameter) throw new Error("Bad parameter") | |
return new Promise(function(resolve, reject){ | |
return 'ok'; | |
}) | |
} | |
try { // this is ugly, we want to avoid this! | |
getPromise3() | |
.then(function(finalResult){console.log("Final result " + finalResult)}) | |
.error(function(e){console.log("Error handler " + e)}) | |
.catch(function(e){console.log("Catch handler " + e)}); | |
} catch (exception) { | |
console.log("ZOMG CRASH!") | |
} | |
// EXAMPLE 4 | |
// EXAMPLE 4 | |
// EXAMPLE 4 | |
// If the function is expecting a Promise to be returned | |
// Promise.reject will allow the error handler to work correctly | |
function getPromise4(someparameter){ | |
if (!someparameter) return Promise.reject(new Error("Bad parameter")) | |
return new Promise(function(resolve, reject){ | |
return 'ok'; | |
}) | |
} | |
getPromise4() | |
.then(function(finalResult){console.log("Final result " + finalResult)}) | |
.error(function(e){console.log("Error handler " + e)}) | |
.catch(function(e){console.log("Catch handler " + e)}); | |
// EXAMPLE 5 | |
// EXAMPLE 5 | |
// EXAMPLE 5 | |
// All toggether now | |
function getPromise(param){ | |
if (!param) { | |
return Promise.reject(Error('bad param')) | |
} | |
return new Promise(function(resolve, reject){ | |
resolve('foo'); | |
}).then(function(result) { | |
console.log('Result 1 ' + result); | |
// We don't need to call Promise.resolve here, the value is already resolved | |
// We can just return it | |
return result; | |
}).then(function(result) { | |
// We can also continue chaining thens as long as we either | |
// 1 - return a value | |
// 2 - return a promise | |
console.log('Result 2 ' + result) | |
// returning a value | |
return result | |
}).then(function(result) { | |
console.log('Result 3 ' + result) | |
// returning another promise | |
return Promise.resolve(someOtherPromise) | |
}).then(function(result) { | |
console.log('Result 4 ' + result) | |
return result + ' resolved' | |
}); | |
} | |
getPromise('something') | |
.then(function(finalResult){console.log("Final result " + finalResult)}) | |
.error(function(e){console.log("Error handler " + e)}) | |
.catch(function(e){console.log("Catch handler " + e)}); | |
// Define another promise here | |
var someOtherPromise = | |
new Promise(function(resolve, reject){ | |
resolve('some other promise!'); | |
}); |
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