Firefox 79 was released on 28th July, 2020. Major web platform updates in this version include :
These operators can be used to perform assignment based on criteria, basesd on whether the left hand side is a falsy, truthy, or nullish value.
// set x to y when x is falsy x ||= y; // set x to y when x is not falsy x &&= y; // set x to y when x is nullish x ??= y;
Read the full Mozilla blog post.