Underscore/Lodash Library. Finally, return the created object. In this example, we ask the user what word needs to be looked up, and then provide the result from an object I've named dictionary . Modify a Property of an Object Literal. As you can see from the example above, this syntax makes adding dynamic properties a two-step process. JavaScript Properties. First, you have to create an object, and then only you can add the dynamic property to it. Alternatively, if you prefer the Underscore library, you can use _.extendOwn (Alias: _.assign) or _.defaults method. But we can’t use them directly as the object’s properties traditionally. For instance, we expect to get Properties names from a user inputting. Properties are the values associated with a JavaScript object. ES6 has brought "Computed property names" that helps in creating an object with dynamic property names. JavaScript provides a bunch of good ways to access object properties. In JavaScript, I’ve created an object like so: var data = { 'PropertyA': 1, 'PropertyB': 2, 'PropertyC': 3 }; Is it possible to add further properties to this object after it’s initial creation if the properties name is not determined until run time? A JavaScript object is a collection of unordered properties. On all subsequent calls, the attribute methods will get called. To add a new property to an object, specify the object name followed by: a dot, the name of the new property, an equals sign, and the value for the new property (enclosed in quotes if it is a string). This example is similar to the above example, but the UNKNOWN method attaches a getter/setter pair of methods for the name triggering the UNKNOWN call. i.e. Sometimes we want to add dynamic properties to an object in JavaScript. When the property name is dynamic or is not a valid identifier, a better alternative is square brackets property accessor: object[propertyName]. They are. Dynamically create Javascript Object. It will return the target object.. Example-1. d = . The process for modifying a property is essentially the same. An object may be redefined dynamically with the prototype property You can add a property directly to an already defined object. 6. Sometimes the property name needs to be stored into a variable. The new object is created normally, the only difference being is that the dynamic key value is to be put between square brackets [ ]. Properties can usually be … The dot property accessor syntax object.property works nicely when you know the variable ahead of time. To dynamically add a property and that it is used by all clones derived from the same object, even if they are created before the property is added, use the reserved word prototype . Both Underscore and Lodash libraries offers several utility methods to add properties to an existing object.. With the Lodash library, you can use any of the _.merge, _.assignIn (alias _.extend), _.assign, or _.defaults method. 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