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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,145 @@ | ||
| "use strict"; | ||
|
|
||
| /** | ||
| * Schedule requests to a function that returns a Promise on a given interval. This is similar to | ||
| * Promise.all(), except that one request is sent after another, leaving a minimum interval | ||
| * (minInterval) between them. | ||
| * | ||
| * This is useful for making API requests without sending every request at once, in order not to | ||
| * exceed the API rate limit. | ||
| * | ||
| * @param {number} minInterval | ||
| * The minimum interval between requests, in milliseconds. | ||
| * | ||
| * @param {function} fn | ||
| * The function to execute. Must return a Promise. | ||
| * | ||
| * @param {...*} params | ||
| * For every parameter required by the function passed to fn, one array is required. Each array | ||
| * must be of the same length, and each element contains the parameters to pass to each request. | ||
| * | ||
| * @returns {Promise<*>} | ||
| * | ||
| * @example | ||
| * // Suppose that we want to call the function makeApiRequest() three times, with a minimum wait | ||
| * // of ten seconds between each call. | ||
| * // | ||
| * // As an example, the signature of makeApiRequest() could be the following: | ||
| * // function makeApiRequest(userID: number, username: string): Promise<Result> | ||
| * // (using TypeScript syntax to illustrate) | ||
| * // | ||
| * // Since our function returns a Promise<Result>, scheduleRequest will return Promise<Result[]>, | ||
| * // Now, let's make the call: | ||
| * | ||
| * scheduleRequests( | ||
| * 10000, | ||
| * makeApiRequest, | ||
| * [ | ||
| * 1, | ||
| * 2, | ||
| * 3 | ||
| * ], | ||
| * [ | ||
| * "Foo", | ||
| * "Bar", | ||
| * "Biz" | ||
| * ] | ||
| * ).then(results => { | ||
| * for (let r of results) { | ||
| * // Handle each result individually. | ||
| * } | ||
| * }).catch(console.error); | ||
| */ | ||
| function scheduleRequests(minInterval, fn, ...params) { | ||
| return new Promise((fulfill, reject) => { | ||
| /* | ||
| * STEP 1: REORGANIZE PARAMS | ||
| * | ||
| * In the example, the user passes two params to the function makeApiRequest: | ||
| * [1, 2, 3] and ["foo", "bar", "biz"]. | ||
| * | ||
| * This gets sent to us in the params variable in the following form: | ||
| * [ | ||
| * [1, 2, 3], | ||
| * ["foo", "bar", "biz"] | ||
| * ] | ||
| * | ||
| * Our goal is to fill the requests variable like this: | ||
| * [ | ||
| * [1, "foo"], | ||
| * [2, "bar"], | ||
| * [3, "biz"] | ||
| * ] | ||
| * | ||
| * With that form, it's easy to make the call to makeApiRequest. | ||
| */ | ||
|
|
||
| let numberOfRequests = null; | ||
| let requests = []; | ||
|
|
||
| for (let i = 0; i < params.length; i++) { | ||
| let paramArr = params[i]; | ||
|
|
||
| if (numberOfRequests === null) { | ||
|
|
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| numberOfRequests = paramArr.length; | ||
|
|
||
| } else if (paramArr.length !== numberOfRequests) { | ||
|
|
||
| return reject(new Error("Parameter length mismatch: the first parameter array " + | ||
| "you passed, has " + numberOfRequests + " elements, but one of the others" + | ||
| " has " + paramArr.length + " elements.")); | ||
|
|
||
| } | ||
|
|
||
| for (let j = 0; j < paramArr.length; j++) { | ||
| let param = paramArr[j]; | ||
|
|
||
| if (typeof requests[j] === "undefined") { | ||
| requests[j] = []; | ||
| } | ||
|
|
||
| requests[j][i] = param; | ||
| } | ||
| } | ||
|
|
||
| /* | ||
| * STEP 2: MAKE THE CALLS | ||
| * | ||
| * Once we have the requests in that format, making the calls is easy. | ||
| * | ||
| * We define a function called makeNextCall which will send the first request. Then, it | ||
| * keep calling itself until no more requests are defined, at which point the function | ||
| * will end by fulfilling the results array. | ||
| */ | ||
|
|
||
| let currentCall = 0; | ||
| let results = []; | ||
|
|
||
| let makeNextCall = function() { | ||
| let start = Date.now(); | ||
|
|
||
| fn(...requests[currentCall]).then(result => { | ||
| results.push(result); | ||
|
|
||
| currentCall++; | ||
|
|
||
| if (requests[currentCall]) { | ||
| // If the elapsed time is less than the minimum interval, | ||
| // wait before making the next call. | ||
| let elapsed = Date.now() - start; | ||
|
|
||
| setTimeout(makeNextCall, minInterval > elapsed ? minInterval - elapsed : 0); | ||
| } else { | ||
| fulfill(results); | ||
| } | ||
|
|
||
| }).catch(reject); | ||
| }; | ||
|
|
||
| makeNextCall(); | ||
|
|
||
| }); | ||
| } | ||
|
|
||
| module.exports = scheduleRequests; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,49 @@ | ||
| <a name="scheduleRequests"></a> | ||
|
|
||
| ## scheduleRequests(minInterval, fn, ...params) ⇒ <code>Promise.<\*></code> | ||
| Schedule requests to a function that returns a Promise on a given interval. This is similar to | ||
| Promise.all(), except that one request is sent after another, leaving a minimum interval | ||
| (minInterval) between them. | ||
|
|
||
| This is useful for making API requests without sending every request at once, in order not to | ||
| exceed the API rate limit. | ||
|
|
||
| **Kind**: global function | ||
|
|
||
| | Param | Type | Description | | ||
| | --- | --- | --- | | ||
| | minInterval | <code>number</code> | The minimum interval between requests, in milliseconds. | | ||
| | fn | <code>function</code> | The function to execute. Must return a Promise. | | ||
| | ...params | <code>\*</code> | For every parameter required by the function passed to fn, one array is required. Each array must be of the same length, and each element contains the parameters to pass to each request. | | ||
|
|
||
| **Example** | ||
| ```js | ||
| // Suppose that we want to call the function makeApiRequest() three times, with a minimum wait | ||
| // of ten seconds between each call. | ||
| // | ||
| // As an example, the signature of makeApiRequest() could be the following: | ||
| // function makeApiRequest(userID: number, username: string): Promise<Result> | ||
| // (using TypeScript syntax to illustrate) | ||
| // | ||
| // Since our function returns a Promise<Result>, scheduleRequest will return Promise<Result[]>, | ||
| // Now, let's make the call: | ||
|
|
||
| scheduleRequests( | ||
| 10000, | ||
| makeApiRequest, | ||
| [ | ||
| 1, | ||
| 2, | ||
| 3 | ||
| ], | ||
| [ | ||
| "Foo", | ||
| "Bar", | ||
| "Biz" | ||
| ] | ||
| ).then(results => { | ||
| for (let r of results) { | ||
| // Handle each result individually. | ||
| } | ||
| }).catch(console.error); | ||
| ``` |
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