equality.md

Equality

In javascript equality comparison can be done using == or ===

1. Loose equality ==: operator will compare for equality after doing any necessary type conversions.

2. Strict Equality ===: operator will not do the conversion, so if two values are not the same type === will simply return false, else compare for equality.

Example 8.0:

var x = 1;
var y = "1";

console.log(x == y) //true --> because type conversion is done and then values are compared

console.log( x === y ) //false  --> because types are different

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Primitive VS non primitive equality:

Its very important to understand how javascript compare primitives and non primitives in a completely different way.

1. Primitives: javascript will compare primitive types by value.

2. Non Primitives: javascript will compare non primitive types by reference, and by reference we mean comparing memory location referenced by that variable.

Example 8.1:

In the example below javascript will compare the values saved in x, y and z

var x = 1;
var y = 1;
var z = 2;

console.log(x == y) //true
console.log(x == z) //false

Example 8.2:

In this example javascript will compare x, y and z by memory location where each variable is referencing.

var x = { first : "Amr" , last : "Labib" };
var y = { first : "Amr" , last : "Labib" };
var z = x;

console.log(x == y) //false because x and y are both referencing a different memory location regardless of the object value.
console.log(x == z) //true because x and z are both referencing the same memory location