Alexander Pushkarev

$breakpoints: (
	'xs': ('(max-width: 576px)'),
	'sm': ('(max-width: 768px)'),
	'md': ('(max-width: 992px)'),
	'lg': ('(max-width: 1199px)'),
);

@mixin respond-to($breakpoint) {
	@if map-has-key($breakpoints, $breakpoint) {
		@media #{inspect(map-get($breakpoints, $breakpoint))} {
			@content;
		}
	} @else {
		@error 'Не указано значение для `#{$breakpoint}`';
	}
}

@include respond-to('md') {
	// ...
}

&:first-child { ... }
&:nth-child(2n) { ... }

.card {
	.image {}
	.link {}
	.description {}
}

@include respond-to('md') {
	.card {
		.image {}
	}
}

@include respond-to('xs') {
	.card {
		.link {}
	}
}

if ( location.pathname == '/pages/page1/' ) {
   $('.obj').css('color', 'red');
}

if ( location.pathname == '/pages/page1/' ) {
   $('.obj').addClass('obj2');
}