Created
July 9, 2019 22:53
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more test code to illustrate Promise, await, and async
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| timeout = 5000 | |
| promiseKeeper = (id) => { | |
| return new Promise((resolve, reject) => { | |
| setTimeout(() => { | |
| resolve(`${id} resolved at ${new Date()}`) | |
| }, timeout); | |
| }) | |
| } | |
| promiseBreaker = (id) => { | |
| return new Promise((resolve, reject) => { | |
| setTimeout(() => { | |
| reject(new Error(`${id} rejected at ${new Date()}`)) | |
| }, timeout); | |
| }) | |
| } | |
| returnsAwaitResultDirectly = async () => { | |
| console.log(await promiseKeeper('A')) | |
| resultB = await promiseKeeper('B') | |
| console.log(resultB) | |
| console.log(`result B is a ${typeof resultB}`) | |
| console.log(await promiseKeeper('C')) | |
| console.log(`returnsAwaitResultDirectly about to await and return at ${new Date()}`) | |
| return await promiseKeeper('D') | |
| } | |
| returnsAwaitResult = async () => { | |
| console.log(await promiseKeeper('A')) | |
| resultB = await promiseKeeper('B') | |
| console.log(resultB) | |
| console.log(`result B is a ${typeof resultB}`) | |
| console.log(await promiseKeeper('C')) | |
| resultD = await promiseKeeper('D') | |
| console.log(`returnsAwaitResult about to return at ${new Date()}`) | |
| return resultD | |
| } | |
| noReturnValue = async () => { | |
| console.log(await promiseKeeper('A')) | |
| resultB = await promiseKeeper('B') | |
| console.log(resultB) | |
| console.log(`result B is a ${typeof resultB}`) | |
| console.log(await promiseKeeper('C')) | |
| console.log(await promiseKeeper('D')) | |
| console.log(`noReturnValue about to exit at ${new Date()}`) | |
| } | |
| // returnsAwaitResultDirectlyResult = returnsAwaitResultDirectly() | |
| // returnsAwaitResultResult = returnsAwaitResult() | |
| // noReturnValueResult = noReturnValue() | |
| waitWaitWait = async () => { | |
| console.log(`### ${new Date()}: about to await returnsAwaitResultDirectly`) | |
| console.log(await returnsAwaitResultDirectly()) | |
| console.log(`### ${new Date()}: about to await returnsAwaitResult`) | |
| console.log(await returnsAwaitResult()) | |
| console.log(`### ${new Date()}: about to await noReturnValue`) | |
| console.log(await noReturnValue()) | |
| console.log(`### ${new Date()}: about to exit waitWaitWait`) | |
| } | |
| // look at waitResult intermittently while waitWaitWait is running. should see that it | |
| // is a Promise, and that it doesn't resolve till after the body of waitWaitWait completes | |
| waitResult = waitWaitWait() | |
| shouldErrorEarly = async () => { | |
| await promiseBreaker('X') | |
| console.log(`made it past rejected awaited promise ${new Date()}`) | |
| return 'ok' | |
| } | |
| shouldErrorEarlyResult = shouldErrorEarly() |
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