Proceed to Checkout Button Label filter » proceedToCheckoutButtonLabel

snippet.js

const { registerCheckoutFilters } = window.wc.blocksCheckout;

// Adjust the proceed to checkout button label.
registerCheckoutFilters( 'example-extension', {
  proceedToCheckoutButtonLabel: ( value, extensions, { cart } ) => {
    if ( ! cart.items ) {
      return value;
    }

    const isSunglassesInCart = cart.items.some(
      ( item ) => item.name === 'Sunglasses'
    );

    // Return the default value if sunglasses is not in the cart.
    if ( ! isSunglassesInCart ) {
      return value;
    }

    return 'Proceed to 😎 checkout';
  }
} );