In javascript equality sign= is used for assigning variables so we use something different to check equality.
In javascript, we have three ways to check equality:
double equals ==
triple equals ===
Object.is()
== (double equals)
Double equals will allow coercion
this is the algorithm for double equals:
1 – if types are the same do the rest of the calculations with triple equals
2 – null and undefined are equal to each other.
3 – if any side is reference type call ToPrimitive()
4 – if we have two different primitive types convert both of them to numbers then do the equality check.
Since double equals allow coercion it allows some corner cases as well
for example
For not dealing with corner cases we shouldn’t use these with double equals:
don’t use 0,””, ” “
don’t use reference types
don’t compare with a boolean
If the types are equal it will send it to triple equals anyway
=== (triple equals)
It doesn’t allow coercion. first, it checks the types if the types are equal it will check values then it will check equality.
Object.is()
It behaves the same as the triple-equals operator except NaN and +0 and -0.
1 === 1; // true
Object.is(1, 1); // true
+0 === -0; // true
Object.is(+0, -0); // false
NaN === NaN; // false
Object.is(NaN, NaN); // true
