javascript演習 4日目/３０日

覚えたこと

reduceの使い方

const totalYears = inventors.reduce((total, inventor) => {
      return total + (inventor.passed - inventor.year);
}, 0);
//他にも重複を数えたり
const transportation = data.reduce(function(obj, item) {
      if (!obj[item]) {
        obj[item] = 0;
      }
      obj[item]++;
      return obj;
}, {});

sortの使い方

const oldest = inventors.sort(function(a, b) {
      const lastInventor = a.passed - a.year;
      const nextInventor = b.passed - b.year;
      return lastInventor > nextInventor ? -1 : 1;
});
//splitとか使って
const alpha = people.sort((lastOne, nextOne) => {
      const [aLast, aFirst] = lastOne.split(', ');
      const [bLast, bFirst] = nextOne.split(', ');
      return aLast > bLast ? 1 : -1;
});

map,filter,textContent,includesの使い方

const category = document.querySelector('.mw-category');
const links = Array.from(category.querySelectorAll('a'));
//もしくは[...category.querySelectorAll('a')]
const de = links
            .map(link => link.textContent)
             .filter(streetName => streetName.includes('de'));