Function checkForUserDefinedFunctions

src/core/friendly_errors/fes_core.js:325–363

     *                      "global mode" and to a p5 instance in "instance mode"
     */
    const checkForUserDefinedFunctions = context => {
      if (p5.disableFriendlyErrors) return;

      // if using instance mode, this function would be called with the current
      // instance as context
      const instanceMode = context instanceof p5;
      context = instanceMode ? context : window;
      const fnNames = entryPoints;

      if (context.preload && !p5.isPreloadSupported()) {
        p5._error(context, translator('fes.preloadDisabled'));
      }

      const fxns = {};
      // lowercasename -> actualName mapping
      fnNames.forEach(symbol => {
        fxns[symbol.toLowerCase()] = symbol;
      });

      for (const prop of Object.keys(context)) {
        const lowercase = prop.toLowerCase();

        // check if the lowercase property name has an entry in fxns, if the
        // actual name with correct capitalization doesnt exist in context,
        // and if the user-defined symbol is of the type function
        if (
          fxns.hasOwnProperty(lowercase) &&
          !context[fxns[lowercase]] &&
          typeof context[prop] === 'function'
        ) {
          const msg = translator('fes.checkUserDefinedFns', {
            name: prop,
            actualName: fxns[lowercase]
          });

          p5._friendlyError(msg, fxns[lowercase]);
        }
      }
    };

    /**
     * Compares the symbol caught in the ReferenceError to everything in