IIRC jQuery started out using string parsing to achieve this but its widespread use prompted browser vendors to add the document.querySelector and document.quer

IIRC jQuery started out using string parsing to achieve this but its widespread use prompted browser vendors to add the document.querySelector and document.querySelectorAll methods to their browsers. Probably in older browsers it still uses the old method but for modern browsers it just passes [selctor] in $("[selector]") through document.querySelectorAll; no string parsing necessary.