1.js

// 1번
const todos = [
  { id: 3, content: 'HTML', completed: false },
  { id: 2, content: 'CSS', completed: true },
  { id: 1, content: 'Javascript', completed: false },
];

const render = todos =>
  todos
    .map(
      ({ id, completed, content }) =>
        `<li id="${id}">
          <label>
            <input type="checkbox"${completed ? ' checked' : ''}>${content}
          </label>
        </li>`
    )
    .join('');

console.log(render(todos));
/*
<li id="3">
  <label><input type="checkbox">HTML</label>
</li>
<li id="2">
  <label><input type="checkbox" checked>CSS</label>
</li>
<li id="1">
  <label><input type="checkbox">Javascript</label>
</li>
*/