Programmatically convert and store unicode strings in Javascript

Context

I'd like to convert strings in javascript to its unicode representation so I can do funky things with it.

Some examples of what I mean:

I can write

eval('\u0076\u0061\u0072 \u006a \u003d \u0022\u0068\u0069\u0022');
// This is `var j = "hi"`.
// For clarity, I kept \u0020 as a space.

I can also write

eval('\u0076\u0061\u0072 \\u006a \u003d \u0022\\u0068\\u0069\u0022');
// Here I've escaped the backslash
// on the variable name and string

These are equivalent, and both result in j == 'hi'.

What's cool is that I can do the following:

var val = '\\u0068\\u0069';
var key = '\\u006a';
eval('\u0076\u0061\u0072 ' + key + ' \u003d \u0022' + val +  '\u0022');

This allows me to generate the values of key and val programmatically, using the following:

function uEncode(str) {
    var hex, i;
    var result = "";
    for (i=0; i < str.length; i++) {
        hex = str.charCodeAt(i).toString(16);
        result += "\\u" + ("000"+hex).slice(-4);
    }
    return result;
}

Question

What I would like to do is to be able to do the following:

eval(uEncode('var j = "hi"'));

This doesn't work because uEncode will escape the backslashes on the var keyword (\u0076\u0061\u0072) and the following characters: = (\u003d), (\u0020), and " (\u0022).

If the the backslashes on the unicode for any javascript keyword or symbol is escaped, eval throws a syntax error.

Unfortunately, this isn't something that can be resolved with a simple

eval(unescape(uEncode('var j = "hi"')));

Is there any way to accomplish this?