Concatenating Javascript Object

Your original code is doing the following:

• Starting a loop, k ;
• Starting a sub-loop, x ;
• Initializing a variable of type array, donutData ;
• Populating donutData with an element via push() method.

Note that for every cycle of k and x , donutData is reset - thus resulting in a variable containing only one element, always.

To solve your problem, reallocate the donutData variable, creating it before you start the loops:

var donutData = [];

for(var k in lista) {
     for(var x in lista[k]){
         donutData.push({label: x, data: lista[k][x], color: "#3c8dbc"});
     }
 }

So the value of donutData will be preserved between iterations of the loops.

You should use push to add elements to an array and it's not worth it to always initialize the variable within the loop:

var donutData = [];
for(var k in lista) {
     for(var x in lista[k]){
         donutData.push({label: x, data: lista[k][x], color: "#3c8dbc"});
     }
 }

This starting from the principle that matches your varable list structure. Note that you will not get the result you want, at least in the field of color , which will always be the same. Without seeing lista , I do not know where to go to get the color inside the lista .