Concat JS not working

Question

var myjson = '{"name": "cluster","children": [';

for (var i = 0; i < unique.length; i++)
{
    var uniquepart = '{"' + unique[i] + '"';
    myjson.concat(uniquepart); 
    var sizepart = ', "size:"';
    myjson.concat(sizepart);
    var countpart = count[i] + '';
    myjson.concat(countpart);
    if (i == unique.length) {
        myjson.concat(" },");
    }
    else {
        myjson.concat(" }");
    }
} 

var ending = "]}";
myjson.concat(ending);

console.log(myjson);

Does anyone know why this string doesn't concat properly and I still end up with the original value?

Answer 1

The concat() method is used to join two or more strings.

Definition and Usage
This method does not change the existing strings, but returns a new string containing the text of the joined strings.
Ref: http://www.w3schools.com/jsref/jsref_concat_string.asp

For example:

myjson = myjson.concat(uniquepart); 

OR

myjson += uniquepart; 

Answer 2

A javascript string is immutable so concat can only return a new value, not change the initial one. If you want to append to a string you have as variable, simply use

myjson += "some addition";