The JavaScript Programming Language

1. It is not possible to modify value of primitve data type

var s = "zdravo";

s.toUpperCase();  // returns ZDRAVO

console.log(s);  //returns 'zdravo'

//Conclusion: Method doesn't change string value.

 

2. Primitive types are changed by value, and object properties are changed by references.

60object_reference.js

//Primitive values are not reference types
var x = 5;
var y = x;
y = 8; //only y is modified. x is not modified
console.log(x); //5



//Objects are reference types
var obj_x = {prop: 13};
var obj_y = obj_x;
obj_y.prop = 21; //obj_x.prop is also modified to 21
console.log(obj_x.prop); //21

 

 

3. Equality

a) Two primitive types are equal if they have same value

b) Two arrays are equal if they have same length and elements have same value

function equalArrays(a,b) {
if (a.length != b.length) return false;
for(var i = 0; i < a.length; i++)
if (a[i] !== b[i]) return false;
return true;
}