Javascript Equality comparison Operator ( "==") or ("===")

Comparison operators compares two values and return a boolean value. equality operators are also comparison operator which checks the equality of values and returns boolean.

in javascript(ES6), There are four(4) which are listed below.

• Using ‘==’ operator
• Using ‘===’ operator
• SameValueZero: used mainly in sets, maps and arrays.
• SameValue: used elsewhere

which operation you choose depend on the type of comparison you are looking to perform.

• double equals (==) will perform a type conversion when comparing two things, and will handle NaN, -0, and +0 specially to conform to IEEE 754 (so NaN != NaN, and -0 == +0);
• triple equals (===) will do the same comparison as double equals (including the special handling for NaN, -0, and +0) but without type conversion; if the types differ, false is returned.
• Object.is does no type conversion and no special handling for NaN, -0, and +0 (giving it the same behavior as === except on those special numeric values).

Strict equality using ('===')

• strict equality compares two values for equality .
• neither values is implicitly converted to some other value before beign compared.
• if values have different types , the values are considered unequal. if the value have the same type , are not numbers and have the same value, they are cosidered equal.
• if both values are numbers, they are considere equal if they are both not NaN and are same value, or if one is +0 and one is -0.
• a values is only equal to itself for all values except number.
• for numbers it is +0===-0. is true
• the only case in which (x!==x) is true is when x is NaN.

Loose Equality using (" == ")

• loos equality compares two values for equality after converting both values to a common type(one or both sides may undergo conversion).
• after conversion , the final equality comparison is performed exactly as === performs it.
• A==B always has identical semantics to (B==A) for any values of A and B .
• undefined and nurll are loosely equal; that is , ( undefined == null) is true. and
• (null == undefined ) is also true. example below

Same-value Equality

• it checks weather two values are functionally identical in all contexts.
• one instance occurs when an attempt to mutate un immutable object property is made.
• this equality is provided with (object.defineProperty())and (Object.is()) methods.