Don’t know why but its shift the clip with cursor.
Premiere Pro CC2020

var myLayers = app.project.activeItem.selectedLayers;
    if (myLayers.length > 0) {
        for (var i = 0; i < myLayers.length; i++) {
        var myProperty = myLayers[i].opacity;
        myProperty.setValueAtTime(myLayers[i].containingComp.time, 0);}
    } 
    else {alert("No layers selected.");}

Thankyou so much!
It is working fine for 1st layer, but I wanted it to applied on selected layer(s).

This is what I tried, but not working :/

var myLayer = app.project.item(index).layer(index).propertySpec;
var myProperty = myLayer.opacity;
myProperty.setValue(50);