Function applyStyling

packages/core/src/render3/node_manipulation.ts:1134–1166

(
  renderer: Renderer,
  isClassBased: boolean,
  rNode: RElement,
  prop: string,
  value: any,
)

 *        otherwise).
 */
export function applyStyling(
  renderer: Renderer,
  isClassBased: boolean,
  rNode: RElement,
  prop: string,
  value: any,
) {
  if (isClassBased) {
    // We actually want JS true/false here because any truthy value should add the class
    if (!value) {
      renderer.removeClass(rNode, prop);
    } else {
      renderer.addClass(rNode, prop);
    }
  } else {
    let flags = prop.indexOf('-') === -1 ? undefined : (RendererStyleFlags2.DashCase as number);
    if (value == null /** || value === undefined */) {
      renderer.removeStyle(rNode, prop, flags);
    } else {
      // A value is important if it ends with `!important`. The style
      // parser strips any semicolons at the end of the value.
      const isImportant = typeof value === 'string' ? value.endsWith('!important') : false;

      if (isImportant) {
        // !important has to be stripped from the value for it to be valid.
        value = value.slice(0, -10);
        flags! |= RendererStyleFlags2.Important;
      }

      renderer.setStyle(rNode, prop, value, flags);
    }
  }
}