Failed: "callback" argument must be a function ERROR

Question

I have a page with a button, which is being controlled by a backend job. once job completes => button gets enabled. user have to manually refresh the page to see the button enabled.

My Goal:

1. Check if the button is enabled
2. If the button is Enabled = exit the function and proceed to the rest of control flow
3. If the button is NOT enabled, wait 10 seconds and refresh the page to check If the button is Enabled, and so on
4. Do not go over 10 iterations of waiting. if the button is still not available - exit the function and fail the test

I'm using Protractor with JavaScript

here is what I have so far:

----------my control flow-----

it ('waiting for button', () => {
        itTopicReg.waitForBtn();
        });

---------my help script from itTopicReg--------

proceedToQaBtn = element(by.buttonText('Proceed to Qa Environment'))
nIntervId = null



 waitForBtn() {
        this.nIntervId = setInterval(this.isBtnEnabled(), 10000);
    };

isBtnEnabled() {
    let count = 0;
    if (this.proceedToQaBtn.isEnabled()) {
         expect(this.proceedToQaBtn.isDisplayed()).toBe(true);
    } else if (count < 10) 
        count++;
        browser.navigate().refresh();
    } else if (count >= 10) {
        clearInterval(this.nIntervId);
    };

I get the following error:

 ✗ waiting for button
            - Failed: "callback" argument must be a function
                at exports.setInterval (timers.js:411:11)
                at ItTopicReg.waitForBtn 

I'm new to Protractor and to JavaScript, pardon if that's something obvious I've searched here and have not found resent clean solution (like Protractor : wait for element to become invisible/hidden or Refreshing page until element appears - JAVA - Selenium)

Answer 1

The first argument passed to setInterval() needs to be a function. Do not call isBtnEnabled, just pass it as an argument:

this.nIntervId = setInterval(this.isBtnEnabled, 10000);
//                          NOTE: no () here ^^

---

As a side note, your enabledness check:

if (this.proceedToQaBtn.isEnabled()) {

has a problem: it will always evaluate to true regardless of the state of the element - isEnabled() returns a promise, which is truthy by definition. If you want to get the actual boolean value of whether the element is enabled or not, resolve the promise:

this.proceedToQaBtn.isEnabled().then(function (isEnabled) {
    if (isEnabled) {
        // ...
    }
});

---

Also, I don't think you should not be using setInterval() at all. Protractor has a built-in mechanism to explicitly wait for and periodically check a specific condition to be met on a page - check out browser.wait() and a set of built-in expected conditions. elementToBeClickable feels like it fits your use case:

var EC = protractor.ExpectedConditions;
browser.wait(EC.elementToBeClickable(this.proceedToQaBtn), 10000);
this.proceedToQaBtn.click();