javascript conditional expression parser

I am working in JavaScript. I want to parse and evaluate conditional expression. ex:

    var param1=1;
    var param2=2;
    var param3=3;
    var expression="(param1==param2)||(param3<param1)";

I want to write a function which will accept 'expression' as a input and parse the expression as well as evaluate expression and return evaluated result.

Please let me know for any suggestions.

Thanks in advance.

Here is the evil one: eval();

var param1=1;
var param2=2;
var param3=3;
var expression=eval("(param1==param2)||(param3<param1)");

Then your function comes,

function myEvaluator(s) {
    return eval(s);
}

You must have variables in expression public.