CODEWITHSUNDEEP
javascriptlodash
user3111277
user3111277

Reputation: 2297

Loop through properties in JavaScript object with Lodash

Is it possible to loop through the properties in a JavaScript object? For instance, I have a JavaScript object defined as this:

myObject.options = {
  property1: 'value 1',
  property2: 'value 2'
};

Properties will get dynamically added to this object. Is there a way for me to just loop through and do a check if a property exists? If so, how?

Upvotes: 159

Views: 218866

Answers (9)

prabhat kumar jena
prabhat kumar jena

Reputation: 13979

If you are checking, if the property exists in the object as stated in the question asked, you can use lodash libray _.has method

_.has(object, path)

Let me give you an example, how to use it.

consider an object

    const user = {
    name : "prabhat",
    age: 27,
    height: "5.7"
   }

if you want to check, if name property exist in the object,you can use _.has method as follows

_.has(user, 'name') //true
_.has(user, 'address') //false

you will get a boolean true/false in return.

Upvotes: 0

danday74
danday74

Reputation: 56956

If you just want to loop through to map property values then use _.mapValues

Upvotes: 0

Kevinleary.net
Kevinleary.net

Reputation: 9670

You can definitely do this with vanilla JS like stecb has shown, but I think each is the best answer to the core question concerning how to do it with lodash.

_.each( myObject.options, ( val, key ) => { 
    console.log( key, val ); 
} );

Like JohnnyHK mentioned, there is also the has method which would be helpful for the use case, but from what is originally stated set may be more useful. Let's say you wanted to add something to this object dynamically as you've mentioned:

let dynamicKey = 'someCrazyProperty';
let dynamicValue = 'someCrazyValue';

_.set( myObject.options, dynamicKey, dynamicValue );

That's how I'd do it, based on the original description.

Upvotes: 10

Akki geek
Akki geek

Reputation: 71

Lets take below object as example

let obj = { property1: 'value 1', property2: 'value 2'};

First fetch all the key in the obj

let keys = Object.keys(obj) //it will return array of keys

and then loop through it

keys.forEach(key => //your way)

just putting all together

Object.keys(obj).forEach(key=>{/*code here*/})

Upvotes: 4

stecb
stecb

Reputation: 14746

Yes you can and lodash is not needed... i.e.

for (var key in myObject.options) {
  // check also if property is not inherited from prototype
  if (myObject.options.hasOwnProperty(key)) { 
    var value = myObject.options[key];
  }
}

Edit: the accepted answer (_.forOwn()) should be https://stackoverflow.com/a/21311045/528262

Upvotes: 45

xoux
xoux

Reputation: 3494

In ES6, it is also possible to iterate over the values of an object using the for..of loop. This doesn't work right out of the box for JavaScript objects, however, as you must define an @@iterator property on the object. This works as follows:

  • The for..of loop asks the "object to be iterated over" (let's call it obj1 for an iterator object. The loop iterates over obj1 by successively calling the next() method on the provided iterator object and using the returned value as the value for each iteration of the loop.
  • The iterator object is obtained by invoking the function defined in the @@iterator property, or Symbol.iterator property, of obj1. This is the function you must define yourself, and it should return an iterator object

Here is an example:

const obj1 = {
  a: 5,
  b: "hello",
  [Symbol.iterator]: function() {
    const thisObj = this;
    let index = 0;
    return {
      next() {
        let keys = Object.keys(thisObj);
        return {
          value: thisObj[keys[index++]],
          done: (index > keys.length)
        };
      }
    };
  }
};

Now we can use the for..of loop:

for (val of obj1) {
  console.log(val);
}    // 5 hello

Upvotes: 1

djechlin
djechlin

Reputation: 60758

Use _.forOwn().

_.forOwn(obj, function(value, key) { } );

https://lodash.com/docs#forOwn

Note that forOwn checks hasOwnProperty, as you usually need to do when looping over an object's properties. forIn does not do this check.

Upvotes: 661

Barry G
Barry G

Reputation: 221

It would be helpful to understand why you need to do this with lodash. If you just want to check if a key exists in an object, you don't need lodash.

myObject.options.hasOwnProperty('property');

If your looking to see if a value exists, you can use _.invert

_.invert(myObject.options)[value]

Upvotes: 0

JohnnyHK
JohnnyHK

Reputation: 311855

For your stated desire to "check if a property exists" you can directly use Lo-Dash's has.

var exists = _.has(myObject, propertyNameToCheck);

Upvotes: 18

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