add new element at the beginning of a JSON

Question

I have this JSON:

var myVar = {
     "9":"Automotive & Industrial",
     "1":"Books",
     "7":"Clothing"
};

I want to add a new element at the beginning, I want to end up having this:

var myVar = {
     "5":"Electronics",
     "9":"Automotive & Industrial",
     "1":"Books",
     "7":"Clothing"
};

I tried this but it is not working:

myVar.unshift({"5":"Electronics"});

Thanks!

An object is an unordered list of key-value-pairs so there is no "beginning" or "end" — Andreas, May 21 '12 at 19:33
This is not JSON. JSON is a string. This is just regular ol' javascript code for an object literal. — Jonathan M, May 21 '12 at 19:34
Check out the following SO question for detail on Objects vs Arrays in javascript, and their various use cases. http://stackoverflow.com/questions/688097/objects-vs-arrays-in-javascript-for-key-value-pairs It seems to me that you just want a nested object with an ID field, perhaps. — dwerner, May 21 '12 at 19:35

score 12 · Answer 1 · edited May 23 '17 at 12:01

Javascript objects don't have an order associated with them by definition, so this is impossible.

You should use an array of objects if you need an order:

var myArray = [
    {number: '9', value:'Automotive & Industrial'},
    {number: '1', value:'Books'},
    {number: '7', value:'Clothing'}
]

then if you want to insert something in the first position, you can use the unshift method of Arrays.

myArray.unshift({number:'5', value:'Electronics'})

//myArray is now the following
[{number:'5', value:'Electronics'},
 {number: '9', value:'Automotive & Industrial'},
 {number: '1', value:'Books'},
 {number: '7', value:'Clothing'}]

more detail here: Does JavaScript Guarantee Object Property Order?

score 2 · Answer 2 · answered May 21 '12 at 19:33

2

There is no way to add new entries to JSON and control the position of them.

If you want to deal with order [strange since objects are unordered], you would have to basically create a new object and append the data.

answered May 21 '12 at 19:33

epascarello

185,306
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score 2 · Answer 3 · answered May 21 '12 at 19:33

Javascript object properties are not deterministically ordered. Properties are accessible no matter what order they're in. If you are depending on them to be in a specific order for a for-in loop, I would suggest rethinking your strategy. Different browsers will take different approaches to ordering the properties. While many browsers will in fact process them in the order you created them, that behavior isn't actually defined in the language spec so you cannot rely on it.

You can use an array of objects, thus controlling order and preserving IDs within the object. — eyelidlessness, May 21 '12 at 19:35

score 2 · Answer 4 · answered May 21 '12 at 20:14

I think the unshift issue might come from the fact that you an associative array. Definition of associative array

This might be a hack but if you MUST have that value at the start of the JSON object, how about:

var myNewVar={'5':'Electronics'};
for (xx in myVar) {
    myNewVar[xx]=myVar[xx];
}

score 2 · Answer 5 · answered Sep 24 '14 at 23:22

This Can be done using the lodash merge function like so:

var myObj = _.merge({ col1: 'col 1', col2: 'col 2'}, { col3: 'col 3', col4: 'col 4' });

Your final object will look like this:

{ col1: 'col 1', col2: 'col 2', col3: 'col 3', col4: 'col 4' }

As others mentioned, there is no guarantee that the order of the keys in the object will remain the same, depending on what you do with it. But, if you perform the merge as your final step, you should be ok. Note, the 'merge' function will produce a completely new object, it will not alter either of the objects you pass into it.

score 1 · Accepted Answer · answered May 21 '12 at 19:37

1

Just do it this way:

var myVar = {
     "9":"Automotive & Industrial",
     "1":"Books",
     "7":"Clothing"
};

// if you want to add a property, then...

myVar["5"]="Electronics"; // note that it won't be "first" or "last", it's just "5"

answered May 21 '12 at 19:37

Jonathan M

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`myVar.5="Electronics";` would cause a syntax error, you'll have to do it like `myVar.["5"]="Electronics";` – Musa May 21 '12 at 19:41

score 0 · Answer 7 · edited Oct 11 '12 at 08:21

0

Try something like that:

myObject.sort(function(a,b) { return parseFloat(a.price) - parseFloat(b.price) } );

or

myObject.sort(function(a,b) { return parseFloat(a.get("price")) - parseFloat(b.get("price")) } );

edited Oct 11 '12 at 08:21

Himanshu Jansari

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answered Oct 11 '12 at 08:02

Valeriane

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score 0 · Answer 8 · answered Apr 19 '21 at 20:25

0

stringify and modify

var foo = {a:1,b:2,c:3};
var bar = JSON.stringify(foo);
foo = JSON.parse('{"d":4,' + bar.slice(1));
alert(JSON.stringify(foo));

answered Apr 19 '21 at 20:25

Nathan Sutherland

935
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add new element at the beginning of a JSON

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