Is it false to say that false in Javascript is still false?

After conducting some research, it appears that the question I have in mind has not been asked before, or maybe it has slipped under my radar.

A rational approach would be to consider the following logic:

false && false === true
false && true === false
true && false === false
true && true === true

HOWEVER

Interestingly, upon testing this logic in javascript using both FireFox and Chrome consoles, I observed different results:

false && false //console output: false
false && true //console output: false
true && false //console output: false
true && true //console output: true

Although a workaround has been found, it still begs the question - why is this happening? One would expect this to follow standard behavior.

It is worth noting that even in the Java documentation, there is mention of logical AND | &&.

javascriptoperatorsboolean-logic

Answer №1

Combining two false statements results in a logically false conclusion.

Answer №2

When dealing with the && operator in an expression, there are specific guidelines that determine the result:

If the left side of the expression is considered "falsey", then the entire expression will ultimately return the value on the left.

In contrast, if the left side of the expression is deemed "truthy", the result will be the value on the right side.

For example, in a scenario like false && false, the left side being "falsey" dictates that the final result will also be false.

To delve further into the intricacies of the || and && operators, I've posted a detailed explanation on my blog.

Answer №3

When utilizing false expressions with AND operators, the overall equation is rendered insignificant because each individual expression must be TRUE for the final result to also be true.

For instance, false && true can be interpreted as follows:

Are both statements accurate? Is "false" AND "true" equivalent to true? If either statement is false, then the entire expression is false.

Consider this other example:

true || (true && false)

In this scenario, the interpretation would be:

Is "true" true OR ... is "true" AND "false" true?

The first statement is determined to be true, thereby negating the necessity to assess the second statement(since one of them has already been proven true), eliminating the need for further evaluation for optimization purposes.

Answer №4

The left-to-right associativity of the && operator means that it evaluates from left to right.

This implies that if the first value is truthy (able to be coerced into true), it will move on to evaluate the second one, and so on until the last one, which ultimately determines the result of the expression.

In this case, since the first element of the operator is falsy (coercible to false), the entire expression immediately returns false.

Learn more about operator precedence from MDN

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