Implementing waitFor functionality with phantomjs-node

Question

I have tried and tested - with success - the phantomjs example waitFor. However, I am having difficulty implementing it via the phantomjs-node module primarily because

Answer 1

Ran into this problem today, thought I'd share my solution.

  // custom helper function
  function wait(testFx, onReady, maxWait, start) {
    var start = start || new Date().getTime()
    if (new Date().getTime() - start < maxWait) {
      testFx(function(result) {
        if (result) {
          onReady()
        } else {
          setTimeout(function() {
            wait(testFx, onReady, maxWait, start)
          }, 250)
        }
      })
    } else {
      console.error('page timed out')
      ph.exit()
    }
  }

The first step is creating a new wait function. It takes the same parameters as the original waitFor function, but works a little differently. Instead of using an interval, we have to run the wait function recursively, after the callback from the test function testFx has been triggered. Also, note that you don't actually need to pass in a value for start, as it gets set automatically.

  wait(function (cb) {
    return page.evaluate(function () 
      // check if something is on the page (should return true/false)
      return something
    }, cb)
  }, function () { // onReady function
    // code
  }, 5000) // maxWait

In this example, I'm setting the callback for testFx function as the callback to page.evaluate, which returns a true/false value based on whether or not it was able to find some element on the page. Alternatively, you could create your callback for page.evaluate and then trigger the testFx callback from it, as shown below:

  wait(function (cb) {
    return page.evaluate(function () 
      // check if something is on the page (should return true/false)
      return something
    }, function(result) {
      var newResult = doSomethingCrazy(result)
      cb(newResult)
    }
  }, function () { // onReady function
    // code
  }, 5000) // maxWait