Yes, there is the W3C (not to be confused with w3schools for the love of God). It is he who defines the patterns of HTML and CSS. In the case of Javascript, who sets the standards is a committee linked to ECMA, an international association similar to ISO. In both cases, decisions are made by committees involving experts in the field, including representatives of browser manufacturers.
However, they basically define syntax patterns, defining what can be used in a given technology or not. This is not the case for things like nomenclature and indentation, which are not officially standardized in the languages cited¹, with the final decision being made by the developers themselves.
¹ In languages like Python indentation is part of the syntax itself, in which case it is defined in the standard.
not to be confused with w3schools +1
– Guilherme Nascimento