Javascript 获取后缀名

function loadFile( file ) {
        const filename = file.name;
        const extension = filename.split( '.' ).pop().toLowerCase();
        if ( extension === 'exr' ) {
                const reader = new FileReader();
                reader.addEventListener( 'load', function ( event ) {
                        handleEXR( event );
                } );
                reader.readAsArrayBuffer( file );
        } else { // 'jpg', 'png'
                const reader = new FileReader();
                reader.addEventListener( 'load', function ( event ) {
                        handleJPG( event );
                } );
                reader.readAsDataURL( file );
        }
}