JavaScript functions for fading layers using various map APIs

README.md

Fade-in layers examples:

• OpenLayers 3
• Leaflet

fadeInLayerLeaflet.js

function fadeInLayerLeaflet(lyr, startOpacity, finalOpacity, opacityStep, delay) {
  let opacity = startOpacity;
  let timer = setTimeout(function changeOpacity() {
    if (opacity < finalOpacity) {
      lyr.setStyle({
        opacity: opacity,
        fillOpacity: opacity
      });
      opacity = opacity + opacityStep
    }
    
    timer = setTimeout(changeOpacity, delay);
  }, delay)
}

fadeInLayerOL3.js

function fadeInLayerOL3(lyr, startOpacity, finalOpacity, opacityStep, delay) {
  let opacity = startOpacity;
  let timer = setTimeout(function changeOpacity() {
    if (opacity < finalOpacity) {
      lyr.setProperties({
        opacity: opacity
      });
      opacity = opacity + opacityStep
    }
    
    timer = setTimeout(changeOpacity, delay);
  }, delay)
}