How can i create this object?

和您做的非常相似：

var obj = { strUserName : { timestamp : point.timestamp , LatLng : point.LatLng }, strUserName : { timestamp : point.timestamp , LatLng : point.LatLng } };

或者更易读：

var obj = {
    strUserName : {
        timestamp : point.timestamp ,
        LatLng : point.LatLng
    },
    strUserName : {
        timestamp : point.timestamp ,
        LatLng : point.LatLng
    }
};

这是一个 对象初始化程序 。它使用给定的属性创建一个新对象（实际上是三个新对象），并返回对最外层对象的引用。

举一些更简单的例子：

// Create a blank object (an object with no properties of its own):
var a = {};

// Create an object with a `name` property with the value "Fred"
var b = {name: "Fred"};

// Create an object with a `foo` property, which is *another* freshly-created
// object with a `name` property with the value "Barney"
var c = {
    foo: {
        name: "Barney"
    }
};

关于您更新的问题：

the username has not worked and im not getting an item for each timestamp, its just overwriting the one entry?

当然是，您在每个循环中覆盖了 history ，而没有将早期的副本存储在任何地方。例如，您可以将它们存储在数组中：

// add history paths and save data
function AddPath( strTag, strUserName, arrayLatLngPoints, pathColour) {

  var historyArray = [];
  for (var i = 0; i < arrayLatLngPoints.length; i++)
    {
    var point = arrayLatLngPoints[i];
    var pos = new google.maps.LatLng(point.lat, point.lng);

    historyArray[i] = {
        strUserName : {
            timestamp : point.timestamp ,
            LatLng : pos
        }
    };

    var date = new Date( parseInt( point.timestamp));
    addMarkers(point.timestamp, point.lat, point.lng, point.timestamp, strUserName, pathColour, date.toString());
    date = null; 
    }
console.log(historyArray);
}

var obj = {strUserName: {timestamp: point.timestamp, lat: point.lat, long: point.long}}