In this post, we will cover only two logical operators - AND(&&) and OR(||).
First, we need to understand the concept of truthy and falsy in JavaScript.
\nAny value that, when converted into a Boolean, becomes true is truthy, while any value that becomes false is falsy.
A Boolean is a logical data type that can only have the values: true or false.
console.log(Boolean(" ")) //false\n\nconsole.log(Boolean(0)) //false\n\nconsole.log(Boolean(false)) //false\n\nconsole.log(Boolean(undefined)) // false\n\nconst name = "Mac"\n\nconsole.log(Boolean(name)) //trueThe AND operator is represented with two ampersands.
In a chain of &&s, each value will be evaluated from left to right. If any of these values happen to be falsy, that value will be returned and the chain will not continue. If the chain doesn’t break before reaching the end, the last value in the chain will be returned.
\nIn other words, AND returns the first falsy value or the last value if none were found.
console.log(`Hemanta` && `Kumar` && `Sundaray`) //Sundaray\n\nconsole.log(1 && false && 3) //falseThe OR operator is written with two pipes.
The || operator behaves exactly like the && does, only in reverse! While a chain of &&s will break if a falsy value is found, a chain of ||s will break when it finds a truthy value. And just like with the &&s, if there are no truthy values and the end of the chain is reached, the last value in that chain is reached.
In other words, a chain of OR returns the first truthy value or the last one if no truthy value is found.
console.log(false || 0 || `text`) //text\n\nconsole.log(false || false || false) //false