Get object keys based on value

问题

I have a use case where I have an object of varying values, and I need to get all of these keys that have a specific value. For instance, here is a sample object:

myObject = {
    Person1: true,
    Person2: false,
    Person3: true,
    Person4: false
};

The key names will vary, but the valid values are true or false. I want to get an array of the names that have a value of true:

myArray2 = [
    'Person1',
    'Person3
];

I've been trying to use various lodash functions in combination such as _.key() and _.filter, but with no luck. How can I accomplish this? I'm open to pure JS or Lodash options.

UPDATE: I accepted mhodges' answer below as the accepted answer, although others gave me the same answer. Based on that, I came up with a Lodash version:

var myArray = _(myObject).keys().filter(function(e) {
    return myObject[e] === true;
}).value();

回答1:

If I understand your question correctly, you should be able to use basic .filter() for this.

myObject = {
    Person1: true,
    Person2: false,
    Person3: true,
    Person4: false
};

var validKeys = Object.keys(myObject).filter(function (key) { 
    return myObject[key] === true; 
});

回答2:

Use Object.keys():

var object = {
    1: 'a',
    2: 'b',
    3: 'c'
};
console.log(Object.keys(object));

Alternative solution:

var keys = [];
for (var key in object) {
    if (object.hasOwnProperty(key)) {
        keys.push(key);
    }        
}    
console.log(keys);

Don't forget to check a key with the help of hasOwnProperty(), otherwise this approach may result in unwanted keys showing up in the result.

回答3:

You can do this with Object.keys() and filter().

var myObject = {
  Person1: true,
  Person2: false,
  Person3: true,
  Person4: false
};

var result = Object.keys(myObject).filter(function(e) {
  return myObject[e] === true;
})
console.log(result)

ES6 version with arrow function

var result = Object.keys(myObject).filter(e => myObject[e] === true)

回答4:

Since Lodash was tagged: With pickBy the values can be filtered (and the keys obtained with _.keys ):

var myArray2  = _.keys(_.pickBy(myObject));

var myObject = {    Person1: true,    Person2: false,    Person3: true,    Person4: false  };
  
var myArray2  = _.keys(_.pickBy(myObject));

console.log(myArray2 );

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

来源：https://stackoverflow.com/questions/42794939/get-object-keys-based-on-value

标签

javascript

arrays

object

lodash