Question

Why is 0 == "" true in JavaScript? I have found a similar post here, but why is a number 0 similar an empty string? Of course, 0 === "" is false.

Answer 1

0 == ''

The left operand is of the type Number.
The right operand is of the type String.

In this case, the right operand is coerced to the type Number:

0 == Number('')

which results in

0 == 0

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From the Abstract Equality Comparison Algorithm (number 4):

If Type(x) is Number and Type(y) is String, return the result of
the comparison x == ToNumber(y).

Source: http://es5.github.com/#x11.9.3