Emulate the with statement

scope.js

function scope(obj, callback) {
    const source = callback.toString();
    const vars = Object.getOwnPropertyNames(obj).map((key) => `${key} = this['${key}']`);
    const body = source.substring(source.indexOf('{') + 1, source.lastIndexOf('}'));
    const fn = new Function(`var ${vars.join(',')}; ${body}`);
    fn.call(obj);
}

// Usage:

const obj = {
    foo: 1,
    bar: 2,
    baz: 3
};

scope(obj, () => {
    console.log(foo + bar + baz); //=> 6
});