JS equality operator detailed _javascript skills

1. Equal = = and unequal!=

Convert operands first and then compare equality

Equality and inequality follow the following rules when converting different data types:

1.1 If one operand is a Boolean, convert it to a numeric value---False to a 0,true conversion to 1 before comparing equality;

1.2 If one operand is a string and the other operand is a numeric value, convert the string to a numeric value before comparing equality

1.3 If an operand is an object, another is not, then the valueof () method of the object is invoked, and the resulting base type value is compared with the preceding rule

1.4 null and undefined are equal.

1.5 You cannot convert null and undefined to any other value until you compare equality

1.6 If an operator is Nan, the equality operator returns FALSE, and the inequality operator returns true, even if the two operands are Nan.

1.7 If two operands are objects, compare whether they point to the same object

An expression	Value
Null = = undefined	True
"Nan" = = Nan	False
5 = = NaN	False
Nan = = Nan	False
Nan!= nan	True
5 = "5"	True
false = = 0	True
true = = 1	True
true = = 2	Flase
Undefined = 0	False
NULL = 0	False

2. Congruent = = and full inequality!==

Two operands equal returns True when not converted, and not equal returns false;

undefined = = Null;//true

Undefined = = null;//false

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