javascript - 返回包含字符串的嵌套数组的最有效方法 (JavaScript)

Question

我想知道是否有一种更有效的方法来基于匹配值访问嵌套数组，而不是使用“forEach”或“for”循环。

这就是我现在所拥有的:

var a = [
  ["aaa", "111", "!!!"],
  ["bbb", "222", "@@@"],
  ["ccc", "333", "###"],
  ["ddd", "444", "$$$"]
];

var b = "222";

var c;

a.forEach((aa) => {
	if (aa.includes(b)) c = aa;
});

// Ideally c would return ["bbb", "222", "@@@"]

console.log(c);

谢谢

Answer 1

我假设您想找到第一个包含针的数组:

var a = [
  ["aaa", "111", "!!!"],
  ["bbb", "222", "@@@"],
  ["ccc", "333", "###"],
  ["ddd", "444", "$$$"]
];



function search(haystack, needle) {
  return haystack.find( item => item.includes(needle) );
}

console.log(search(a,'222'));

如果你的数据是静态的，你可以创建一个缓存，并使用needle来获取数组。

var a = [
  ["aaa", "111", "!!!"],
  ["bbb", "222", "@@@"],
  ["ccc", "333", "###"],
  ["ddd", "444", "$$$"]
];

const cache = a.reduce(
  (out, row) => {
    for (const item of row) out[item] = row;
    return out;
  },
  Object.create(null)
);


console.log(cache['222']);

现代 ES2019 版本，使用 flatMap 和 Map:

const a = [
  ["aaa", "111", "!!!"],
  ["bbb", "222", "@@@"],
  ["ccc", "333", "###"],
  ["ddd", "444", "$$$"]
];

const m = new Map(a.flatMap(r=>r.map(i=>[i,r])));

console.log(m.get('222'));