Js對象怎么通過value值拿到key值

var data = { a: 1, b: 'string', c: {}, d: {a: 98, b: 'str'} } function findKey (value, compare = (a, b) => a === b) { return Object.keys(data).find(k => compare(data[k], value)) } var val = data.b findKey(val) // b