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A simple utility for Node.js to wait until a predicate function returns truthy before moving on; for use with ES6 async/await syntax.
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| /** | |
| * Utility that waits for @predicate function to return truthy, testing at @interval until @timeout is reached. | |
| * | |
| * Example: await until(() => spy.called); | |
| * | |
| * @param {Function} predicate | |
| * @param {Number} interval | |
| * @param {Number} timeout | |
| * | |
| * @return {Promise} | |
| */ | |
| async function until(predicate, interval = 500, timeout = 30 * 1000) { | |
| const start = Date.now(); | |
| let done = false; | |
| do { | |
| if (predicate()) { | |
| done = true; | |
| } else if (Date.now() > (start + timeout)) { | |
| throw new Error(`Timed out waiting for predicate to return true after ${timeout}ms.`); | |
| } | |
| await new Promise((resolve) => setTimeout(resolve, interval)); | |
| } while (done !== true); | |
| } | |
| module.exports = until; |
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