javascript - Replacing a property value in JSON - Stack Overflow

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If I have a JSON structure that looks something like this:

var user = {
    map: {
        width: 785,
        height: 791
    },
    image: {
        name: "image.png",
        size: {width:32}
    },
    properties:[{
        firstName: "Bob",
        lastName: "Jones",
    }]
};

How would I change (after creation) the value of the firstName property to "Jane"?

I am fairly new to JSON, and I'm just trying to figure out how to make this one change for now. Any help would be greatly appreciated.

If I have a JSON structure that looks something like this:

var user = {
    map: {
        width: 785,
        height: 791
    },
    image: {
        name: "image.png",
        size: {width:32}
    },
    properties:[{
        firstName: "Bob",
        lastName: "Jones",
    }]
};

How would I change (after creation) the value of the firstName property to "Jane"?

I am fairly new to JSON, and I'm just trying to figure out how to make this one change for now. Any help would be greatly appreciated.

• javascript
• json

Share Improve this question Follow edited Jun 21, 2011 at 0:05 alex 491k204204 gold badges889889 silver badges991991 bronze badges asked Jun 20, 2011 at 23:45 simmBsimmB 3111 gold badge11 silver badge44 bronze badges 2

• You don't need a function, you should be able to change it with user.properties[0].firstName = "Jane". – Zachary Commented Jun 20, 2011 at 23:48
• 1 Instead of changing the title to indicate "Resolved", the way to close a question on StackOverflow is to click the checkmark to the left of one of the answers you received to designate that as your "Accepted" answer. :o) – user113716 Commented Jun 21, 2011 at 0:00

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4 Answers 4

Sorted by: Reset to default 7

Well, one reason for your confusion might be that this is not JSON at all. JSON is a text format used for serialising objects. This is just a literal object in Javascript.

To change the firstName property, you would access the first item in the properties array in the user object:

user.properties[0].firstName = "Jane";

As long as the user variable is in scope:

user.properties[0].firstName = "Jane";

var changeName = function(obj, newName) {
   obj.properties[0].firstName = newName;
   return obj;
}

I saw this question and the solutions to it but my script still didn't work. I found the solution and I figured I should post this here, it might save some people a little research.

My JSON result had some integers in it and it required the parseInt() function.

Taking the above example you probably have to do something like this.

user.map.width = parseInt(somevariable);

Since javascript is loosely typed I never really worry about it, but in this case it's necessary.

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