cycle.js-如何获取集合项中的集合长度

你可以用镜片 makeCollection isLast

function omit(obj, key) {
    let tmp = { ...obj }; //Copy the object first
    delete tmp[key];
    return tmp;
}

const listLens = {
   get: stateArray => stateArray.slice(0, -1).concat({
            ...stateArray[stateArray.length - 1],
            isLast: true
        }),
   set: (stateArray, mappedArray) => mappedArray.slice(0, -1)
           .concat(omit(mappedArray[mappedArray.length - 1], 'isLast'))
};

const List = isolate(
    makeCollection({
        item: Child,
        itemKey: (childState, index) => String(index),
        itemScope: key => key,
        collectSinks: instances => ({
            onion: instances.pickMerge('onion'),
            DOM: instances.pickCombine('DOM')
                .map(itemVNodes => ul(itemVNodes))
        })
    }),
    { onion: listLens, '*': null }
);

itemScope

itemScope: key => ({ onion: myLens, '*': key })