Javascript - 从值中打印枚举的名称

Question

有没有办法打印给定 int 值的枚举字段的值？例如我有以下枚举:

refractiveIndex = {"vacuum": 1, "air": 1.000293, "water": 1.33, "diamond": 2.419};

如果我有一个值，有没有办法打印枚举的名称。例如，假设我有一个变量设置为 1，我想打印出“vacuum”，我该怎么做:

var value = 1;
console.log(refractiveIndex(value)); // Should print "vacuum" to console

?

Answer 1

您可以迭代键并针对属性的值进行测试。

var refractiveIndex = {"vacuum": 1, "air": 1.000293, "water": 1.33, "diamond": 2.419},
    value = 1,
    key;

Object.keys(refractiveIndex).some(function (k) {
    if (refractiveIndex[k] === value) {
        key = k;
        return true;
    }
});
console.log(key);

ES6

var refractiveIndex = {"vacuum": 1, "air": 1.000293, "water": 1.33, "diamond": 2.419},
    value = 1,
    key = Object.keys(refractiveIndex).find(k => refractiveIndex[k] === value);

console.log(key);