eventually

eventually.js

var MAX_TIME_TO_WAIT = 10; // ms

// Tests for the eventual satisfaction of a set of expectations. Returns
// a Promise that resolves if the given function runs without errors and
// rejects if resolution cannot be obtained within `MAX_TIME_TO_WAIT` ms.
function eventually(expectations) {
  var timeStarted = Date.now();
  new Promise(function (resolve, reject) {
    function testExpectationsAndResolve() {
      try {
        expectations();
        resolve(); // Resolve if no exception is thrown
      } catch (error) {
        var timeSpent = Date.now() - timeStarted;
        if (timeSpent > MAX_TIME_TO_WAIT) {
          // Pass along the error if we've timed out
          reject(error);
        } else {
          // Otherwise try again
          setTimeout(testExpectationsAndResolve);
        }
      }
    }
    
    setTimeout(testExpectationsAndResolve);
  });
}