The context evaluation factory getEvaluator()

function writeVars(contextObject) { var vars = ""; if(contextObject != null && typeof contextObject == "object") { const regVar = /^(var |let |const )?([a-zA-z_$][a-zA-z_$0-9]*)$/; for(let i = 0, keys = Object.keys(contextObject), length = keys.length; i < length; i++) { var a = regVar.exec(keys[i]); vars += (a[1]?a[1]:"var ") + a[2] + " = arguments[0]['" + keys[i] + "'];"; } } return vars; } function getEvaluator() { return eval("(function()\ {" + writeVars(arguments[0]) + "return function(){return eval('('+arguments[0]+')');}\ });")(arguments[0]); } const Evaluator = '(' + getEvaluator + ')';

A Local Context Evaluation Factory and Evaluator

function Test() { // This Z would be in the evalautor's context but it is overriden // in a nested scope. var Z = 100; (function(){ // Here the scope is local, not global. var Z = 0; // used since Z is local // local but not used since b is overriden by the context object. var b = 9; // In evaluator context, b is a const and c is a var. // eval(Evaluator) is the local context evaluation factory. const evaluator = eval(Evaluator)({"const b":2, c:3}); // sum is the copy a function, and lives in the evaluator's context. const sum = evaluator(function(a){return a + b + c + Z}); // const b = 2, var c = 3 and Z = 0 are in the evaluator's context. console.log(sum(1)); // 1 + 2 + 3 + 0 = 6 // setB is the copy a function, and lives in the evaluator's context. const setB = evaluator(function(value){b = value}); try { // Attempt to change const b in evaluator's context to 100. setB(100); } catch(e) { console.log(e.message); // invalid assignment to const 'b' } })(); }