How to pass var by parameter or reference in javascript

referenceVsParameter.js

/* =================================
Pass by parameter
================================= */
function par(e) {
  e = "bar";
}

var a = "foo";
par(a);
console.log("a: "+a); // "foo"

/* =================================
Pass by reference
================================= */
function ref(e) {
  e.ref = "bar"
}

var b = {}
b.ref = "foo";
ref(b);

console.log("b.ref: "+b.ref); // "bar"