将对象推入数组

Question

My understanding of JS objects is weak. If I pass a set of objects into a new array, then try and get the length or value at a certain index (as extract below) I return an undefined message. Is there an obvious mistake here? Thanks.

var arrayTest = [];
var objCollection = obj.name + obj.size + obj.weight; 
arrayTest.push(objCollection);
alert(arrayTest[0]); // returns undefined

To clarify, I'm collecting a customer's product selection and returning its technical data stored in a json file - with the intention of placing this selection into a table.

{
"name": "the name",
"size": "the size",
"weight": "the weight"
},

Answer 1

Are you sure objCollection actually contains a value? It looks to me like one of the fields of the obj object is undefined as concatenating a value with an undefined object yields undefined. And thus, you push an undefined object to your array instead of what you want. See Bergi's comment for correction.