You can use a for.in loop in a function to check if an object is empty. In this article, we will explore how to use the forEach method to get values by key from an array of objects. When dealing with arrays of objects, we often want to access a specific value based on its key. If the object is empty, the length of the returned array will be 0: Object.keys(value).length = 0 J avaScript is a popular programming language and the forEach method is a handy tool for iterating over arrays. If you know the value you are checking is an object, you can use Object.keys to return an array of a passed-in object’s property names. The methods also have different efficiencies in terms of operations per second, which could be important if you are checking many values. The method you choose to use depends on whether you know if the value to check will be an object. There are various ways to check if an object is empty. I'd opt for a reduce solution, which can simply ignore the property or even set you up with a default value.You want to check if an object, for example, an object returned from a fetch request, is empty. If not explicitly checked whether or not the columns exists, it'll throw an error and (at best) provide you with undefined. While map is a proper solution to select 'columns' from a list of objects, it has a downside. If you're a little more into functional programming, take a look at Ramda's R.pluck() function, which would look something like this: var result = R.pluck('foo')(objArray) // or just R.pluck('foo', objArray) Var result = _.map(objArray, _.property()) īoth _.map() calls in the above example will return. Var result = _.map(objArray, _.property('someProperty.aNumber')) _.property(), and hence _.map(), also allow you to provide a dot-separated string or array in order to access sub-properties: var objArray = [ Var result = _.map(objArray, _.property('foo')) As a result, the following two lines are equivalent to the code sample above from pre-Lodash 4. _.property() is a shorthand function that returns a function for getting the value of a property in an object.Īdditionally, _.map() now allows a string to be passed in as the second parameter, which is passed into _.property(). Update 2: As Mark points out in the comments, somewhere between Lodash v4 and 4.3, a new function has been added that provides this functionality again. _.pluck() is still available in Underscore. Update: _.pluck() has been removed as of Lodash v4.0.0, in favour of _.map() in combination with something similar to Niet's answer. Both do exactly what you want in a single function call! var result = _.pluck(objArray, 'foo')

Check out Lodash's _.pluck() function or Underscore's _.pluck() function.

For each javascript object