创建具有可变属性的对象

Question

I'm trying to do this:

var sortAfter = req.query.sortAfter || '_id';
var ascending = req.query.direction || -1;
var sorted = {sortAfter: ascending};

But a console.log(sorted) output the following object:

{ sortAfter: -1 }

It's like the first variable is not used in the object creation...

Question: How do i get the object to be made of two variables, and not one variable and one fixed string?

Answer 1

try this way:

var sortAfter = req.query.sortAfter || '_id';
var ascending = req.query.direction || -1;
var sorted = {};
sorted[sortAfter] = ascending;

Answer 2

In object literals, the keys are always literals, they're never variables. If you want to set a dynamic object key, you'll have to do it like this:

var sorted = {};
sorted[sortAfter] = ascending;

Answer 3

Use the subscript/bracket notation:

var sorted = {};
sorted[sortAfter] = ascending;

The subscript operator will convert its operand to a string,