.dev/assets/admin/js/customize/controls/range-control.js
( function( $, api ) {
api.bind( 'ready', function() {
$( '.range_control__reset' ).on( 'click', function() {
const rangeContainer = $( this ).parent();
const rangeInput = rangeContainer.find( 'input[data-input-type="range"]' );
const controlValue = rangeContainer.find( '.range_control__value' );
const defaultValue = rangeInput.data( 'default-value' );
rangeInput.val( defaultValue );
controlValue.find( 'span' ).html( defaultValue );
controlValue.find( 'input' ).val( defaultValue );
const customizeSetting = controlValue.find( 'input' ).data( 'customize-setting-link' );
wp.customize.control( customizeSetting ).setting.set( defaultValue );
} );
} );
}( jQuery, wp.customize ) );