JavaScript push to array

How do I push new values to the following array?

json = {"cool":"34.33","alsocool":"45454"}

I tried json.push("coolness":"34.33");, but it didn't work.

It's not an array.

var json = {"cool":"34.33","alsocool":"45454"};
json.coolness = 34.33;

or

var json = {"cool":"34.33","alsocool":"45454"};
json['coolness'] = 34.33;

you could do it as an array, but it would be a different syntax (and this is almost certainly not what you want)

var json = [{"cool":"34.33"},{"alsocool":"45454"}];
json.push({"coolness":"34.33"});

Note that this variable name is highly misleading, as there is no JSON here. I would name it something else.

var array = new Array(); // or the shortcut: = []
array.push ( {"cool":"34.33","also cool":"45454"} );
array.push (  {"cool":"34.39","also cool":"45459"} );

Your variable is a javascript object {} not an array [].

You could do:

var o = {}; // or the longer form: = new Object()
o.SomeNewProperty = "something";
o["SomeNewProperty"] = "something";

and

var o = { SomeNewProperty: "something" };
var o2 = { "SomeNewProperty": "something" };

Later, you add those objects to your array: array.push (o, o2);

Also JSON is simply a string representation of a javascript object, thus:

var json = '{"cool":"34.33","alsocool":"45454"}'; // is JSON
var o = JSON.parse(json); // is a javascript object
json = JSON.stringify(o); // is JSON again

That is an object, not an array. So you would do:

var json = { cool: 34.33, alsocool: 45454 };
json.supercool = 3.14159;
console.dir(json);

object["property"] = value;

or

object.property = value;

Object and Array in JavaScript are different in terms of usage. Its best if you understand them:

Object vs Array: JavaScript

Use the push() function to append to an array:

// initialize array
var arr = [    "Hi",    "Hello",    "Bonjour"];

// append new value to the array
arr.push("Hola");

Now array is

var arr = [
    "Hi",
    "Hello",
    "Bonjour"
    "Hola"
];

---

// append multiple values to the array
arr.push("Salut", "Hey");

Now array is

var arr = [
    "Hi",
    "Hello",
    "Bonjour"
    "Hola"
    "Salut"
    "Hey"
];

---

// display all values
for (var i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}

Will print:

Hi
Hello
Bonjour
Hola 
Salut
Hey

Update

If you want to add the items of one array to another array, you can use Array.concat:

var arr = [
    "apple",
    "banana",
    "cherry"
];

arr = arr.concat([
    "dragonfruit",
    "elderberry",
    "fig"
]);

---

console.log(arr);

Will print

["apple", "banana", "cherry", "dragonfruit", "elderberry", "fig"]