Is it possible to create a variable from user-written data about it?

Question

JavaScript

How to create a variable from user input? For example
var [user-entered variable name] = [user-entered variable value]

Answer 1

var a = 'varname';
var str = a+' = '+'123';
eval(str)
alert(varname);

Answer 2

var customerInput = [];
customerInput[varName] = varValue;

Answer 3

jsfiddle.net/koceg/uryrvos5