Please explain me this

I have this code:

var text = "{meth: 'adder', operand1: 2, operand2: 3};";
var jObject;
eval('jObject = '+ text);
eval(jObject.meth + '(' + jObject.operand1 + ',' +
jObject.operand2 + ');');
function adder(op1, op2)
{
var sum = op1 + op2;
alert(op1 + " + " + op2 + " = " + sum);
}

Code (markup):

I know what the eval function do but I don't understant how "meth,operand1,operand2" become properties of the object jObject.(yes i get that JObject take the text from var text).
What is the role of ":" and "{" in this case;

 

{ .... } is a shorthand way to define array values.

Essentially, its converting meth: 'adder', eval it so it's a key value or an associative array:

so you can do alert(jObject.meth); alert(jObject.operand1); alert(jObject.operand2);

It just starts out with an array of strings, then converts them to an associative array