对象值未正确更新

Question

I have an object as follows:

{
"headerSection": {
    "text": "Some Text",
    "color": "red",
    "fontSize": "12px",
    "backgroundColor": "#000",
    "textAlign": "left"
   }
}

I have a dropdown list which users can choose a different font size ie 14px, 16px .. 20px . On the change event of this dropdown I want to change the value of fontSize in my above object so for that I do:

$('#font-size-ddl').change(function () {
    var value = $(this).val();
    headerObj.fontSize = value;
    console.log(JSON.stringify(headerObj));
});

In the above console.log the output is:

{
"headerSection": {
    "text": "Some Text",
    "color": "red",
    "fontSize": "12px",
    "backgroundColor": "#000",
    "textAlign": "left"
 },
"fontSize": "20px",
}   

Can someone please tell me what I am doing wrong.

Answer 1

You should update headerSection fontSize property.

In your case the compiler looking after fontSize property of your headerObj object, it don't found it and create a new property for your object.

 let headerObj={ "headerSection": { "text": "Some Text", "color": "red", "fontSize": "12px", "backgroundColor": "#000", "textAlign": "left" } } $('select').change(function () { var value = $(this).val(); headerObj.headerSection.fontSize = value; console.log(JSON.stringify(headerObj)); }).trigger('change'); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <select> <option value="20px">20px</option> <option value="30px">30px</option> </select> 

Answer 2

I believe, after looking at your output, that the fontSize property is being improperly appended.

You need to do this to add it under headerSection .

$('#font-size-ddl').change(function () {
    var value = $(this).val();
    headerObj.headerSection.fontSize = value; // like this
    console.log(JSON.stringify(headerObj));
});

Answer 3

$('#font-size-ddl').change(function () { 
    var value = $(this).val(); 
    headerObj.headerSection.fontSize = value;
    console.log(JSON.stringify(headerObj));
 });

you're adding a value to headerObj instead of headerObj.headerSection, as you can see from the console.log

Answer 4

You have a nested object. An unnested object would look like this

{
"text": "Some Text",
"color": "red",
"fontSize": "12px",
"backgroundColor": "#000",
"textAlign": "left"
}

Instead you have an outside object, with a property called "headerSection" pointing at another object. If you're not going to change your data structure, then you need to change your code to access the inner property. Something like this

$('#font-size-ddl').change(function () {
  var value = $(this).val();
  headerObj["headerSection"]["fontSize"] = value;
  console.log(JSON.stringify(headerObj));
});

Answer 5

Ok then you just need to make a little change.

$('#font-size-ddl').change(function () {
    var value = $(this).val();
    headerObj.headerSection.fontSize = value;  // See here.
    console.log(JSON.stringify(headerObj));
});