Removing the event listeners in Javascript

Question

When a button is clicked and a function is executed which is consisting of sub-functions and event listeners. Consider this:

function init() {
  canvas = document.getElementById("canvas");
  context = canvas.getContext('2d');
  context.strokeStyle = 'purple';
  context.lineWidth = 6;
  context.lineCap = 'round';
  canvas.addEventListener('mousedown', dragStart);
  canvas.addEventListener('mousemove', drag);
  canvas.addEventListener('mouseup', dragStop);
}

Is there a way to remove this event listeners as soon as the function exited or when another function is called?