Can I replace this by var in Javascript objects

Answer 1

Your question is not really clear ^^

This is this, and can't be assigned (sort of constant, but not strictly imutable as its value depends of context).

You could "replace this by a variable" (since you shorten "var" and aren't talking about the keyword) in a sense. It will be local to the constructor function, and only accessible from inside, not outside... but could be used to implement kind of protected properties:

function MyO() {
this.val = 42;
var local_val = "forty-two";
Object.defineProperty(this,"prop", {
get: function() { return local_val; },
set: function(str) {
if (typeof str=='string') local_val = str;
else throw new Error('prop accept only string');
}

var o = new MyO();
console.log(o.val); // 42
o.val = 'foo';
console.log(o.val); // foo

console.log(o.local_val); // undefined

console.log(local_val); // undef var error

console.log(o.prop); // forty-two
o.prop = 'bar';
console.log(o.prop); // bar
o.prop = 42;
console.log(o.prop); // custom error