How to prepend i.e. a .js class to the first level of a nested selector in SASS.

prepend-selector-to-nesting.scss

/**
 * Prepend a selector to the first level of nested selectors.
 * Comments demonstrate compiled CSS.
 */
.foo {
    /* .foo */
    
	.bar {
		/* .foo .bar */
		
		.js & { /* .js .foo .bar */ }
		
		&.foobar {
		
			.js & { /* .js .foo .bar.foobar */ }
		}
	}
}