Select Missing Footage In Comp

/* This script selects all layers with missing footage in the current composition. */
app.beginUndoGroup("Select Missing Footage");

var comp = app.project.activeItem;
if (comp && comp instanceof CompItem) {
  var layers = comp.layers;
  for (var i = 1; i <= layers.length; i++) {
    var layer = layers[i];
    var source = layer.source;
    if (source && source.hasOwnProperty('footageMissing') && source.footageMissing) {
      layer.selected = true;
    } else {
      layer.selected = false;
    }
  }
} else {
  alert("Please select a composition.");
}

app.endUndoGroup();