var ralphaStart = /^[a-z]/, // The regex visualized: // // /----------\ // | | /-------\ // | / Top \ | | | // /--- Border ---+-| Right |-+---+- Width -+---\ // | | Bottom | | // | \ Left / | // | | // | /----------\ | // | /-------------\ | | |- END // | | | | / Top \ | | // | | / Margin \ | | | Right | | | // |---------+-| |-+---+-| Bottom |-+----| // | \ Padding / \ Left / | // BEGIN -| | // | /---------\ | // | | | | // | | / Min \ | / Width \ | // \--------------+-| |-+---| |---/ // \ Max / \ Height / rautoPx = /^(?:Border(?:Top|Right|Bottom|Left)?(?:Width|)|(?:Margin|Padding)?(?:Top|Right|Bottom|Left)?|(?:Min|Max)?(?:Width|Height))$/; export function isAutoPx( prop ) { // The first test is used to ensure that: // 1. The prop starts with a lowercase letter (as we uppercase it for the second regex). // 2. The prop is not empty. return ralphaStart.test( prop ) && rautoPx.test( prop[ 0 ].toUpperCase() + prop.slice( 1 ) ); }