PolyCoder Fun for Typescript/Javascript

Functional

FuncValue

A FuncValue<T> represents a value that could require to call a function to be obtained. Function getValue allows to get the actual value from a FuncValue, whether it is a direct value or a function that returns the value.

Examples:

const value1: FuncValue<string> = "directValue"
const value2: FuncValue<string> = () => "deferredValue"

interface MyConfig {
  connectionString: FuncValue<string>;
  maxConnections: FuncValue<number>;
}

getValue

Returns the actual value from a given FuncValue.

Examples:

console.log(getValue('directValue'))
// Prints: 'directValue'

console.log(getValue(() => 'deferredValue'))
// Prints: 'deferredValue'

getValueOrDefault

Returns the actual value from a given FuncValue, if given. In the case of null or undefined are given, the same falsy value is returned.

Examples:

console.log(getValue(undefined))
// Prints: undefined

console.log(getValue(null))
// Prints: null

console.log(getValue('directValue'))
// Prints: 'directValue'

console.log(getValue(() => 'deferredValue'))
// Prints: 'deferredValue'

FuncPromise

Works the same as FuncValue<T> but with the possibility to be a Promise<T> or a function that returns one. In fact it is defined as:

type FuncPromise<T> = FuncValue<T> | FuncValue<Promise<T>>;

Examples:

const value1: FuncPromise<string> = "directValue"
const value2: FuncPromise<string> = () => "deferredValue"
const value3: FuncPromise<string> = Promise.resolve("deferredValue")
const value4: FuncPromise<string> = async () => "deferredValue"

getValueAsync

Returns a promise for the actual value from a given FuncPromise.

Examples:

console.log(await getValue('directValue'))
// Prints: 'directValue'

console.log(await getValue(() => 'deferredValue'))
// Prints: 'deferredValue'

console.log(await getValue(Promise.resolve('directPromise')))
// Prints: 'directPromise'

console.log(await getValue(() => Promise.resolve('deferredPromise')))
// Prints: 'deferredPromise'

getValueAsyncOrDefault

Returns the actual value from a given FuncPromise, if given. In the case of null or undefined are given, the same falsy value is returned.

Examples:

console.log(getValue(undefined))
// Prints: undefined

console.log(getValue(null))
// Prints: null

console.log(getValue('directValue'))
// Prints: 'directValue'

console.log(getValue(() => 'deferredValue'))
// Prints: 'deferredValue'

Promises

delay

Returns a promise that resolves after given milliseconds

Examples

await delay(500)
// awaits for 500 ms

tryPromise

Wraps the execution of a function to capture any result or thrown error into a Promise.

Examples

tryPromise(() => a / b))
  .then(response => ...)
  .catch(error => ...)
// When b is zero, the error is captured into the promise

getAllPages

Given a function that is capable of retrieving a page of items and a continuation token, loops until the continuation token gets undefined, in which case all the pages get concatenated into the result.

Examples

async function fetchPage(continuationToken) {
  const response = await fetch(`http://.../items?token=${continuationToken}`)
  const result = await response.json()
  return [result.items, result.nextToken || undefined]
}

const allItems = await getAllPages(fetchPage)