title: Dart/Flutter check if value is an integer/whole number
body: <p>How do I check if a value is a whole number (integer) or contains a decimal? In Javascript we have <code>isInteger</code> but I couldn't find the equivalent in Dart.</p>
  
  <p>We seem to have checks for <code>isEven</code>, <code>isOdd</code>, <code>isFinite</code>, <code>isInfinite</code>, <code>isNaN</code> and <code>isNegative</code> but no <code>isInteger</code>?</p>