Method implicitLoopWhen

src/core/runtime/runtime.js:588–606

* Iterate over targets with a when condition, applying forward or reverse per element. * Supports async conditions transparently -- returns a Promise if any condition is async.

(targets, whenExpr, context, forwardFn, reverseFn)

         * Supports async conditions transparently -- returns a Promise if any condition is async.
         */
        implicitLoopWhen(targets, whenExpr, context, forwardFn, reverseFn) {
            var elements = [];
            this.implicitLoop(targets, function (elt) { elements.push(elt); });

            var conditions = elements.map(function (elt) {
                context.beingTested = elt;
                return whenExpr.evaluate(context);
            });
            context.beingTested = null;

            var hasPromise = conditions.some(function (c) { return c && typeof c.then === "function"; });
            if (hasPromise) {
                return Promise.all(conditions).then((results) => {
                    context.result = this.#applyWhenResults(elements, results, forwardFn, reverseFn);
                });
            } else {
                context.result = this.#applyWhenResults(elements, conditions, forwardFn, reverseFn);
            }
        }

        #applyWhenResults(elements, results, forwardFn, reverseFn) {
            var matched = [];