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Boolean logic

The boolean logic is simply operators who returns an boolean true or false, we use this syntax most of the time for conditional.

The AND operator

The and operator is represent with this syntax && for this return true the all the conditions that you create must be true otherwise the AND operator will return false:

let age = 23;

if ( age >= 20 && age < 30 ) {
    return `You're a man now !!`;
} else {
    return "You're still a child";
}
  1. In this example we create a variable to test our AND operator, we give to this variable the value 23.
  2. We now use an if / else statement to check something, with the AND operator we need to have the conditions true and in this example it's okay because age is greater than 20 and also inferior at 30 so our both conditions our true the result will be You're a man now !!.
  3. If one of our conditions will be not true the result will be You're still a child.

The OR operator

We saw above the AND operator who check if all the conditions are true, well with the OR operator is a little bit different you can have only one conditions true for this return true.

let age = 23;

if ( age >= 20 || age <= 15 ) {
    return `You're a man now !!`;
} else {
    return "You're still a child";
}
  1. We will use the same code than above for our demo, to use the OR operator you have to use this || syntax which is not the l letter in lowercase.
  2. In this condition we ask if age is greater than 20 and the answer is yes OR if age is inferior than 15 which is false so we can see our if like this (true || false). The result of this condition will be You're a man now.
  3. Like we said earlier with the OR operator as long as one condition is true the result will always be true.

The NOT operator

The NOT operator is different from the two above because this one will not check if this condition is true or false or everything else this operator will simply inverse the actual value:

let isAdult = true;

if ( !isAdult ) {
    return "You're still a child";
} else {
    return `You're a man now !!`;
}
  1. We create a new variable isAdult and we give this variable a boolean true.
  2. In the if / else statement we ask if isAdult is equal to true which is in this case yes, but you may notice that we also use this ! syntax who is equal to the NOT operator and inverse the value, so in this case the isAdult variable is now equal to false so the result will be You're still a child.

Current errors

This is a list of the main errors that you can meet:

Note: I'm not a wizard there is maybe some issue that you notice above so fell free to open an issue in the github repo if you find a new error not mentioned above.

← If / else statementsFunction →