JavaScript Object - Different Type Depending on Context

Question

I am going to start off by saying that I don't think this is possible, but hoping that someone knows some special way in JavaScript to do this. I have a JavaScript object defined as follows:

var t = {
  "fields": {
    "a": ["99", "98"]
  }
};

I am looking for a way so that I can define the same element of an array twice with different values that could be used in two different contexts - something like this:

var t = {
  "fields": {
    "a": ["99", "98"],
    "a": "99|98"
  }
};

If I was to query it using the syntax t.fields["a"] it would return "99|98" but if I was to query it using t.fields["a"][0] then it would return "99". I understand if I query an array without specifying an index then it returns "99,98" as a string - but I need it to return the entries delimited with a "|" instead of a ",".

Answer 1

It's also possible to use a getter function, like this:

var t = {
    "fields": {
        "_a": ["99", "98"],
        "a": function (index) {
            if (typeof index != 'undefined')
                return this._a[index];
            else
                return this._a.join('|');
        }
    }
};

console.log(t.fields['a']()); // 99|98
console.log(t.fields['a'](1));// 98

You can also have a global get function for all the fields:

var t = {
    "fields": {
        "_a": ["99", "98"],
        get: function (field, index) {
            if (typeof index != 'undefined')
                return this['_' + field][index];
            else
                return this['_' + field].join('|');
        }
    }
};

console.log(t.fields.get('a')); // 99|98
console.log(t.fields.get('a', 1)); // 98