javascript - 使用 JavaScript 中的值获取属性

Question

我有一个列出 keyCodes 的对象:

var keyCodes = {
    "a": 97, "b": 98, "c": 99, "d": 100, "e": 101, "f": 102,
    "g": 103, "h": 104, "i": 105, "j": 106, "k": 107, "l": 108,
    "m": 109, "n": 110, "o": 111, "p": 112, "q": 113, "r": 114,
    "s": 115, "t": 116, "u": 117, "v": 118, "w": 119, "x": 120,
    "y": 121, "z": 122
};

但我需要引用值，而不是属性。我能做多高效 这没有重写整个对象？

Answer 1

生成一个新对象，其中属性名称是值，值是属性名称，其中使用 Array#reduce和 Object.keys生成新对象的方法。

var keyCodes = {
    "a": 97, "b": 98, "c": 99, "d": 100, "e": 101, "f": 102,
    "g": 103, "h": 104, "i": 105, "j": 106, "k": 107, "l": 108,
    "m": 109, "n": 110, "o": 111, "p": 112, "q": 113, "r": 114,
    "s": 115, "t": 116, "u": 117, "v": 118, "w": 119, "x": 120,
    "y": 121, "z": 122
  };

var res = Object.keys(keyCodes).reduce(function(obj, k) {
  obj[keyCodes[k]] = k;
  return obj;
}, {})

console.log(res[121])
console.log(res[106])
console.log(res[110])