custom eleventy filter to count posts by year #eleventy #ssg

.eleventy.js

//...
eleventyConfig
        .addFilter('yearTags', posts => {
            const yearsList = posts.map(p => p.data.date.getFullYear())
            const yearsCount = {}
            yearsList.forEach(y => {
                if (!yearsCount[y]) yearsCount[y] = 1
                else yearsCount[y]++
            });
            return Object.keys(yearsCount)
                .map(yc => ({ name: yc, count: yearsCount[yc] }))
        });
//...