javascript - How does a Js object get the key value through the value value?

Question

Generally, the value can be obtained through obj.key, but if I want to do the reverse, what should I do?

Answer 1

The mapping from

key to value is one-way, and value is not unique.
So there is no problem in getting value from key, but not vice versa.

Answer 2

for...inLoop object judgment and acquisition?

Answer 3

I have a stupid method

Traverse the object, determine whether the value of the current object is equal to the value to be checked, and if it matches the output key

Answer 4

The output value is not unique. It can be obtained by value.

Answer 5

For reference, if you use lodash, you can directly use _.findKey

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

// 自定义比较函数，比如结合 lodash 可以
findKey({a: 98, b: 'str'}, _.isEqual) // d

Answer 6

Can I recycle it? Take out $.each like this