如何在散列中将变量值分配为变量名？

Question

I need to define a hash for posting some ajax data using jQuery. The hash will look something like:

var setname = 'set_1';
elements = { set_1: {'beer','water','wine'} };

The challenge I need to solve is 'set-1' (the key of Array elements) should be dynamically named based on the value of var setname .

I want to avoid using eval() of course.. in PHP it can be done using the double dollar sign like this: $$setname , but what's the way to do this in JavaScript?

Answer 1

You can do what you'd like to like so:

var setname = 'set_1', elements = {};
elements[setname] = ['beer','water','wine'];
alert(elements['set_1']); // beer,water,wine

See this in action at http://jsfiddle.net/x5KRD/ .

All objects in JS can be accessed using dot notation ( obj.method() or obj.property ), or bracket notation ( obj['method']() or obj['property'] ). Using bracket notation lets you dynamically specify method/property/key names.

For example, while clumsy, window['alert']('hi') is equivalent to window.alert('hi') .

Note that your code won't work as-is, anyways, because you're using object literal notation ( {'beer','water','wine'} ) to contain an array (it should be in square brackets ['beer','water','wine'] instead). Object literals need to have key-value pairs.

Answer 2

var setname = 'set_1', 
    elements = {};

elements[setname] = ['beer','water','wine'];

Answer 3

You have to understand that there's really no such thing as "JSON notation" in Javascript - it's native Javascript notation that we're talking about. What jQuery wants is a Javascript value for the POST data, not necessarily a Javascript object constant.

Thus, your code will prepare your POST data like this:

var elements = {};
elements[setName] = { /* something */ };
elements[somethingElse] = { /* something else */ };

and so on. When you're ready to do the POST, you'd just use "elements":

$.post(url, elements, function() { /* callback code */ });

Answer 4

Directly use the identifier in square brackets :

const setname = 'set_1';
const elements = { [setname]: ['beer','water','wine'] }

Please bear in mind the usage of square brackets for lists