Always use === to compare with 0

src/ol/coordinate.js

@@ -66,7 +66,7 @@ ol.coordinate.closestOnSegment = function(coordinate, segment) {
   var y2 = end[1];
   var dx = x2 - x1;
   var dy = y2 - y1;
-  var along = (dx == 0 && dy == 0) ? 0 :
+  var along = (dx === 0 && dy === 0) ? 0 :
       ((dx * (x0 - x1)) + (dy * (y0 - y1))) / ((dx * dx + dy * dy) || 0);
   var x, y;
   if (along <= 0) {

src/ol/map.js

@@ -1265,7 +1265,7 @@ ol.Map.prototype.renderFrame_ = function(time) {
     Array.prototype.push.apply(
         this.postRenderFunctions_, frameState.postRenderFunctions);
 
-    var idle = this.preRenderFunctions_.length == 0 &&
+    var idle = this.preRenderFunctions_.length === 0 &&
         !frameState.animate &&
         !frameState.viewHints[ol.ViewHint.ANIMATING] &&
         !frameState.viewHints[ol.ViewHint.INTERACTING];

src/ol/mapbrowserevent.js

@@ -323,7 +323,7 @@ ol.MapBrowserEventHandler.prototype.isMouseActionButton_ =
   if (ol.LEGACY_IE_SUPPORT && ol.IS_LEGACY_IE) {
     return pointerEvent.button == 1;
   } else {
-    return pointerEvent.button == 0;
+    return pointerEvent.button === 0;
   }
 };