I’m working with a JavaScript object and need some help with a specific requirement.
let dataObject = {"name": "John", "age": "25"}
I want to add another property that has the same key as an existing one, so the final result would look like this:
let dataObject = {"name": "John", "age": "25", "name": "Mike"}
When I try using dataObject["name"] = "Mike", it just replaces the original value instead of creating a duplicate key. How can I achieve this behavior in JavaScript? Is there a way to have multiple properties with identical keys in a single object?
yup, js objects only keep the last key if they’re duplicates. best bet is to switch to an array of objs like [{“name”: “John”}, {“name”: “Mike”}] or maybe a Map for more flexibility!
Nope, you can’t do this with regular JavaScript objects. JSON doesn’t allow duplicate keys - when you parse JSON with duplicates, only the last value survives. I hit this exact problem with API responses that had repeated field names. JavaScript object literals work the same way as JSON here. Duplicate keys always overwrite the previous ones. If you need multiple values with the same identifier, use a different structure. Make each key point to an array of values, or build something more nested depending on what you’re doing. JavaScript objects are basically hash maps, and hash maps need unique keys to work.
JavaScript objects are designed so that each key must be unique, meaning that if you assign a new value to an existing key, it will overwrite the previous one. This is consistent across JavaScript and many other programming languages. To represent multiple values for the same key, you might consider restructuring your data. For instance, you could use an array as a value, like {“name”: [“John”, “Mike”], “age”: “25”}, or use different keys to distinguish them, such as {“firstName”: “John”, “lastName”: “Mike”, “age”: “25”}. The choice depends on your specific requirements.