Array Math

Array.prototype.diff = function(arr2) { return this.filter(x => !arr2.          includes(x)); }
 let arr1 = ['release','layer-1','bsp-1']
 console.log(`OG list: ${arr1}`);
 let arr2 = ['release','layer-2','bsp-1']
 console.log(`New list: ${arr2}`);

 console.log(`Remove list: ${arr1.diff(arr2)}`);
 let newDl = arr2.diff(arr1);
 console.log(`New downlowd list: ${newDl}`);
 console.log(`Refresh list: ${arr2.diff(newDl)}`);