primitives_vs_objects.js

/*
Primitives are stored as copies
*/

//declare and initialize a variable
var string = 'string';
//we copy the variable's value into a new variable
var hood = string; 
//check that they are the same
console.log(hood === string)                //true
//modify the value of the first variable
string = 'new string';
//the copy does not change
console.log(hood)                         //'string'
console.log(string)                       // 'new string'

/*
Objects are stored as references
*/

//initialize a variable to refer/point to an array
var a = [1, 2, 3];
//share the reference with another variable; there is only one array in memory
//we simply create a second pointer to this single array and call it b
var b = a;
//check that they are the same 
console.log(b === a)     // true
//modify the array using the original reference
a[0] = 99; 
// display the changed array [99, 2, 3] using the new reference
console.log(a)  // [99, 2, 3]
console.log(b)  // [99, 2, 3]

/* What happened? 
Here we mutated the object a; we did not REBIND the object a which is why a and b still point to the same object
When we change the properties of an object, we mutate the object
Mutating the object does not change the links between the pointers and the object
*/


//initialize a variable to refer/point to an array
var a = [1, 2, 3];
//copy the reference into another variable
var b = a;
//check that they are the same 
console.log(b === a)     // true
//modify the array using the original reference
a = [504, 345]; 
console.log(b === a)   //false
// display the changed array using the new reference
console.log(a)        // [504, 345]
//b still points to the original array value; b is not affected by a's reassignment
console.log(b)        // [1, 2, 3]



/*
What happened here?
We rebound/reassigned the pointer a to an entirely new array
Rebinding a means that the link between a and [1, 2, 3] has been severed

*/