javascript1.js

function changeValue(val) {
    val = val + " changed";
    console.log(val); //A changed
}

var val = "A";
changeValue(val);
console.log(val); //A

//----------------------------

function changeObj(obj) {
    obj.oldProp = 'older';
    obj.newProp = 'new Prop';
}

var obj = { oldProp: "old" };
changeObj(obj);
console.log(obj.hasOwnProperty('newProp')); //true 
console.log(obj.oldProp); //older