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JavaScript: Logical operators and Boolean Values

Banesa Guaderrama on November 15, 2018

Logical Operators ! (NOT), && (AND), || (OR) If you are learning to code or new to coding, you will be using logical operators, these ar...
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André Michel Andy •

Great article! Don't forget that && and || use short-circuit evaluation, useful for use cases like feature flags and set default values:

//if flag is true, then execute this function
process.env.FLAG && someFunc();

//Instead of...
const var2 = var1 ? var1 : "something";
//...use || operator
const var2 = var1 || "something";
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Guillaume F. •

Yes!

As a reminder, the logical operators work the following way with non-boolean values:

expr1 && expr2: If expr1 is truthy, returns expr2; else, returns expr1.
expr1 || expr2: If expr1 is truthy, returns expr1; else, returns expr2.

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Banesa Guaderrama •

Hi André! Thank you for your comment. With just some lines you have provided a great input about default values.

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Peter Kim Frank •

Great post! Just a heads up that you can highlight code like so if you'd like:

code block with no colors example

code block with colors example

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Banesa Guaderrama •

Hi Peter! Thanks for the advise, I for sure will start doing it.

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Alex Lohr •

The bitwise operator ^ (XOR) can also be used to evaluate if only one of both given expressions is true and can be a useful shorthand:

x ^ y === Number(x && !y || !x && y)

Since it is not a logical operator, it will cast to Number (0 = false, 1 = true), but if will accept any true-ish value, so you only need to cast to boolean if you actually require the result to be one.

Unfortunately, there's no logical XOR operator in JS as of now.

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Banesa Guaderrama •

Thanks for your input Alex! You have made more robust the post with your comment, I appreciate you took the time.