Question

when constructing an object using methods from other objects as an attribute name get Syntax Error: Unexpected token . – cannot find correct syntax

var R = function(a) { this.arg = a; };
R.prototype.name = function() { return this.arg; }

var r1 = new R('abc');
var name1 = r1.name();        // => "abc"

var o1 = { 'abc': r1 }        // this works with constant
var o2 = { name1: r1 }        // does not work with variable (see answer)
var o3 = { r1.name(): r1 }    // this fails - syntax
var o4 = { 'abc': r1.name() } // this works

have tried { (r1.name()): r1 }, but that fails as well.

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please note that strings and integers are evaluated as barewords whereas methods and variables are not:

var o5 = { e.1: 123 }          // fails
var o6 = { 'e.1': 123 }        // succeeds
var o7 = { 1: 123 }            // succeeds
var o8 = { '1': 123 }          // same as o7

Answer 1

var o2 = { name1: r1 }        // this works with variable

This has the same meaning as:

var o2 = { 'name1': r1 }

In other words, it’s still treating name1 as a literal string. The key in an object literal must be a constant or a so-called “bareword” — this is a restriction of the language. Variables and function invocations cannot be used as keys in object literals (but they can be used as values). Using variables will appear to work, but the variable name will be used as the key and not the variable’s value.

You will have to do something like:

var o2 = {};
o2[name1] = r1;

var o3 = {};
o3[r1.name()] = r1;