Is there a way to use variable keys in a JavaScript object literal?

In ES6, use computed property names.

const key = "anything";   

const object = {   
    [key]: "key attribute"
//  ^^^^^  COMPUTED PROPERTY NAME
};

Note the square brackets around key. You can actually specify any expression in the square brackets, not just a variable.

On modern Javascript (ECMAScript 6) you can sorround the variable with square brackets:

var key = "anything";

var json = {
    [key]: "key attribute"
};

Yes. You can use:

var key = "anything";
var json = { };
json[key] = "key attribute";

Or simply use your second method if you have the values at hand when writing the program.

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