( пример работы jsfiddle здесь )
var sample_operation_member = {"x": 100, "y": 250};
var sample_undo_member = { "operation" : [sample_operation_member, sample_operation_member,sample_operation_member] };
var hist = {
"undo": [
sample_undo_member,
sample_undo_member,
sample_undo_member,
sample_undo_member
]
}
alert(hist.undo[0].operation[0].x);
Или, более подробно:
var hist = {
undo: [
{"operation": [{"x": 100, "y":100},{"x": 100, "y":100},{"x": 100, "y":100}]},
{"operation": [{"x": 100, "y":100},{"x": 100, "y":100},{"x": 100, "y":100}]},
{"operation": [{"x": 100, "y":100},{"x": 100, "y":100},{"x": 100, "y":100}]},
{"operation": [{"x": 100, "y":100},{"x": 100, "y":100},{"x": 100, "y":100}]}
]
}
alert(hist.undo[0].operation[0].x);