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index.js
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index.js
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/**
* @param {function} func - function to execute
* @param {number|function(number):number} intervalLength - length in ms to wait before executing again
* @param {{iterations: Infinity|number, stopOnError: boolean}} [options]
*
* @returns {Promise} Promise object with no result
*/
function interval(func, intervalLength, options = {}) {
validateArgs(func, intervalLength, options)
const defaults = {
iterations: Infinity,
stopOnError: true
}
const settings = Object.assign(defaults, options)
return new Promise((rootPromiseResolve, rootPromiseReject) => {
const callFunction = currentIteration => {
// Set up a way to track if a "stop" was requested by the user function
let stopRequested = false
const stop = () => {
stopRequested = true
}
// Set up a function to call the next iteration. This is abstracted so it can be called by .then(), or in .catch(), if options allow.
const callNext = () => {
// If we've hit the desired number of iterations, or stop was called, resolve the root promise and return
if (currentIteration === settings.iterations || stopRequested) {
rootPromiseResolve()
return
}
// Otherwise, call the next iteration
callFunction(currentIteration + 1)
}
// Calculate our interval length
const calculatedIntervalLength = (typeof intervalLength === 'function') ? intervalLength(currentIteration) : intervalLength
// If the interval length was calculated, validate the result
if (typeof intervalLength === 'function') {
if (!Number.isInteger(calculatedIntervalLength) || calculatedIntervalLength < 0) {
rootPromiseReject(new Error('Function for "intervalLength" argument must return a non-negative integer.'))
return
}
}
// Call the user function after the desired interval length. After, call the next iteration (and/or handle error)
setTimeout(() => {
const returnVal = func(currentIteration, stop)
if (!(returnVal instanceof Promise)) {
rootPromiseReject(new Error('Return value of "func" must be a Promise.'))
return
}
returnVal.then(callNext).catch(err => {
if (!settings.stopOnError) {
callNext()
return
}
rootPromiseReject(err)
})
}, calculatedIntervalLength)
}
callFunction(1)
})
}
/**
* A helper function to validate the arguments passed to interval(...)
*
* @param {*} func
* @param {*} intervalLength
* @param {*} options
*/
function validateArgs(func, intervalLength, options) {
// Validate "func"
if (typeof func !== 'function') {
throw new TypeError('Argument 1, "func", must be a function.')
}
// Validate "intervalLength"
if (typeof intervalLength === 'number') {
if (!Number.isInteger(intervalLength) || intervalLength < 0) {
throw new TypeError('Argument 2, "intervalLength", must be a non-negative integer or a function that returns a non-negative integer.')
}
} else if (typeof intervalLength !== 'function') {
throw new TypeError('Argument 2, "intervalLength", must be a non-negative integer or a function that returns a non-negative integer.')
}
// Validate options...
if (typeof options !== 'object') {
throw new TypeError('Argument 3, "options", must be an object.')
}
// Validate passed keys
const allowedKeys = ['iterations', 'stopOnError']
Object.keys(options).forEach(key => {
if (!allowedKeys.includes(key)) {
throw new TypeError('Option "' + key + '" is not a valid option.')
}
})
// validate "iterations" option (if passed)
if (options.hasOwnProperty('iterations')) {
if (options.iterations !== Infinity && (!Number.isInteger(options.iterations) || options.iterations < 1)) {
throw new TypeError('Option "iterations" must be Infinity or an integer greater than 0.')
}
}
// validate "stopOnError" option (if passed)
if (options.hasOwnProperty('stopOnError')) {
if (typeof options.stopOnError !== 'boolean') {
throw new TypeError('Option "stopOnError" must be a boolean.')
}
}
}
module.exports = interval