Nightmare action to check if an element is in the viewport

Nightmare-InViewport.js

Nightmare.action('inViewport', function(selector, done) {
    this.evaluate_now(function(selector) {
        var element = document.querySelector(selector);

        if (!element){
            return false;
        }

        var rect = element.getBoundingClientRect();

        var height = Math.max(document.documentElement.clientHeight, window.innerHeight || 0);
        var width = Math.max(document.documentElement.clientWidth, window.innerWidth || 0);

        return !(rect.top >= height || rect.bottom <= 0 ||
        	rect.left >= width || rect.right <= 0);
    }, done, selector);
});

// Example with chai.js

nightmare
	.inViewport('.my-button')
	.then((isInViewport) => {
		expect(isInViewport).to.be.true;
	});