ember-in-viewport/addon/utils/is-in-viewport.js

Detect if an Ember View or Component is in the viewport @ 60FPS

const defaultTolerance = {
  top: 0,
  left: 0,
  bottom: 0,
  right: 0,
};

export default function isInViewport(
  boundingClientRect = {},
  height = 0,
  width = 0,
  tolerance = defaultTolerance
) {
  const { top, left, bottom, right, height: h, width: w } = boundingClientRect;
  const tolerances = Object.assign(
    Object.assign({}, defaultTolerance),
    tolerance
  );
  const {
    top: topTolerance,
    left: leftTolerance,
    bottom: bottomTolerance,
    right: rightTolerance,
  } = tolerances;

  return (
    top + topTolerance >= 0 &&
    left + leftTolerance >= 0 &&
    Math.round(bottom) - bottomTolerance - h <= Math.round(height) &&
    Math.round(right) - rightTolerance - w <= Math.round(width)
  );
}