Define local variables from a map.

gistfile1.js

// Bad behaviour ahead!
// doesn't work with strict mode.

function local(obj) {
  	var global = Function("return this")();
	var tmpName = "_tmp";
	while (tmpName in global) {
		tmpName = "_"+tmpName;
	}
	global[tmpName] = obj;

	var defineString = "var "+Object.keys(obj).join(", ")+";\n";
	defineString +="(function() {\n\tvar global = Function('return this')();\n\t";
	for (var key in obj) {
		defineString += "\t" + key +" = global."+tmpName+"['" + key + "'];\n"
	}
	defineString += "\tdelete global['"+tmpName+"']\n})();\n"
	return defineString;
}

// example:

function bob() {
   eval(local({
     a: 23,
     b: 40
   }));
   
   return a * b;
}

console.log(bob());