saleor-dashboard/src/components/Skeleton.tsx

import { makeStyles } from "@saleor/macaw-ui";
import classNames from "classnames";
import React from "react";

const useStyles = makeStyles(
  theme => ({
    "@keyframes skeleton-animation": {
      "0%": {
        opacity: 0.6
      },
      "100%": {
        opacity: 1
      }
    },
    primary: {
      "&$skeleton": {
        background: theme.palette.primary.main
      }
    },
    skeleton: {
      animation: "skeleton-animation .75s linear infinite forwards alternate",
      background: theme.palette.background.default,
      borderRadius: 4,
      display: "block",
      height: "0.8em",
      margin: "0.2em 0"
    }
  }),
  { name: "Skeleton" }
);

interface SkeletonProps {
  className?: string;
  primary?: boolean;
  style?: React.CSSProperties;
  children?: React.ReactNode;
}

const Skeleton: React.FC<SkeletonProps> = props => {
  const { className, primary, style, children } = props;

  const classes = useStyles(props);

  return children ? (
    (children as React.ReactElement)
  ) : (
    <span
      data-test-id="skeleton"
      className={classNames(classes.skeleton, className, {
        [classes.primary]: primary
      })}
      style={style}
    >
      &zwnj;
    </span>
  );
};

Skeleton.displayName = "Skeleton";
export default Skeleton;