As you can see from the example above, this syntax makes adding dynamic properties a two-step process. 1) Object.assign() The Object.assign() method is used to copy the values of all properties from one or more source objects to a target object. Underscore/Lodash Library. ES6 has brought "Computed property names" that helps in creating an object with dynamic property names. Ask Question Asked 5 years, 3 months ago. It will return the target object.. Example-1. 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. Finally, return the created object. 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). dynamicvar~new d~foo = 123 say d~foo 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 . On all subsequent calls, the attribute methods will get called. 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? The new object is created normally, the only difference being is that the dynamic key value is to be put between square brackets [ ]. JavaScript provides a bunch of good ways to access object properties. Live Demo 6. Otherwise, add a property with the specified value to the object. The process for modifying a property is essentially the same. First, you have to create an object, and then only you can add the dynamic property to it. A JavaScript object is a collection of unordered properties. d = . Given the example in the jsFiddle (updated here), this would produce the following structure: The dot property accessor syntax object.property works nicely when you know the variable ahead of time. Properties are the values associated with a JavaScript object. An object may be redefined dynamically with the prototype property You can add a property directly to an already defined object. Sometimes the property name needs to be stored into a variable. When the property name is dynamic or is not a valid identifier, a better alternative is square brackets property accessor: object[propertyName]. 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 . JavaScript Properties. Sometimes we want to add dynamic properties to an object in JavaScript. There are two methods to merge properties of javascript objects dynamically. For instance, we expect to get Properties names from a user inputting. But we can’t use them directly as the object’s properties traditionally. They are. Properties can usually be … 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. i.e. An object may be written that can dynamically add methods to itself. Modify a Property of an Object Literal. Alternatively, if you prefer the Underscore library, you can use _.extendOwn (Alias: _.assign) or _.defaults method. 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