想問的是有關於match用法

範例1(這個我沒問題)

const input = "As I was going to Saint Ives";
const reg = /\w{3,}/ig;
input.match(reg);    //["was","going","Saint","Ives"]

範例2(這裡不大懂)

const html = `<a class="foo" href="/foo" id="foo">Foo</a>\n` +
            `<A href ='/foo' Class="foo">Foo</a>\n` +
            `<a href="/foo">Foo</a>\n` +
            `<a onclick="javascript:alert('foo!')" href="/foo">Foo</a>`;
function sanitizeATag(aTag){
    const parts = aTag.match(/<a\s+(.*?)>(.*?)<\/a>/i);
    console.log(parts);
}

sanitizeATag(html);
/*
結果:
[
  '<a class="foo" href="/foo" id="foo">Foo</a>',
  'class="foo" href="/foo" id="foo"',
  'Foo',
  index: 0,
  input: '<a class="foo" href="/foo" id="foo">Foo</a>\n' +
    `<A href ='/foo' Class="foo">Foo</a>\n` +
    '<a href="/foo">Foo</a>\n' +
    `<a onclick="javascript:alert('foo!')" href="/foo">Foo</a>`,
  groups: undefined
]
*/

不大懂為什麼範例2,JS怎麼去解讀它?
懇請各位先進不吝指教,我想過1天了,還是看不大懂..