javascript - How do I set the value property in AngularJS' ng-options?

Question

Here is what seems to be bothering a lot of people (including me).

When using the ng-options directive in AngularJS to fill in the options for a <select> tag, I cannot figure out how to set the value for an option. The documentation for this is really unclear - at least for a simpleton like me.

I can set the text for an option easily like so:

ng-options="select p.text for p in resultOptions"

When resultOptions is for example:

[
    {
        "value": 1,
        "text": "1st"
    },
    {
        "value": 2,
        "text": "2nd"
    }
]

It should be (and probably is) the most simple thing to set the option values, but so far I just don't get it.

Answer 1

See ngOptions

ngOptions(optional) – {comprehension_expression=} – in one of the following forms:

For array data sources: label for value in array select as label for value in array label group by group for value in array select as label group by group for value in array track by trackexpr For object data sources: label for (key , value) in object select as label for (key , value) in object label group by group for (key, value) in object select as label group by group for (key, value) in object

In your case, it should be

array = [{ "value": 1, "text": "1st" }, { "value": 2, "text": "2nd" }];

<select ng-options="obj.value as obj.text for obj in array"></select>

Update

With the updates on AngularJS, it is now possible to set the actual value for the value attribute of select element with track by expression.

<select ng-options="obj.text for obj in array track by obj.value">
</select>

How to remember this ugly stuff

To all the people who are having hard time to remember this syntax form: I agree this isn't the most easiest or beautiful syntax. This syntax is kind of an extended version of Python's list comprehensions and knowing that helps me to remember the syntax very easily. It's something like this:

Python code:

my_list = [x**2 for x in [1, 2, 3, 4, 5]]
> [1, 4, 9, 16, 25]

# Let people to be a list of person instances
my_list2 = [person.name for person in people]
> my_list2 = ['Alice', 'Bob']

This is actually the same syntax as the first one listed above. However, in <select> we usually need to differentiate between the actual value in code and the text shown (the label) in a <select> element.

Like, we need person.id in the code, but we don't want to show the id to the user; we want to show its name. Likewise, we're not interested in the person.name in the code. There comes the as keyword to label stuff. So it becomes like this:

person.id as person.name for person in people

Or, instead of person.id we could need the person instance/reference itself. See below:

person as person.name for person in people

For JavaScript objects, the same method applies as well. Just remember that the items in the object is deconstructed with (key, value) pairs.