JavaScript - logical operators

Logical operators are used to combine two or more conditions. JavaScript has following logical operators:

&& - logical AND operator
|| - logical OR operator
! - logical NOT operator

Logical AND operator (&&)

The logical AND operator is used to combine two or more conditions and returns true only when all conditions are true, otherwise returns false. Consider the example below to understand this concept:

function range_func(x){
  //&& operator is used to combine conditions
  //returns true only when x >= 10 and x <= 25
  if(x >= 10 && x <= 25)
    return x + " belongs to range [10, 25].<br>"; 
  else
    return x + " do not belongs to range [10, 25].<br>";
}

var txt;
txt = range_func(15);
txt = txt + range_func(25);
txt = txt + range_func(50);

The output (value of txt) after running above script will be:

15 belongs to range [10, 25].
25 belongs to range [10, 25].
50 do not belongs to range [10, 25].

Logical OR operator (||)

The logical OR operator is used to combine two or more conditions and returns true when any of the conditions is true, otherwise returns false. Consider the following example:

function range_func(x){
  //|| operator is used to combine conditions
  //returns true when either x < 100 or x > 200
  if(x < 100 || x > 200)
    return x + " do not belongs to range [100, 200].<br>";  
  else
    return x + " belongs to range [100, 200].<br>";
}

var txt;
txt = range_func(50);
txt = txt + range_func(100);
txt = txt +  range_func(150);

The output (value of txt) after running above script will be:

50 do not belongs to range [100, 200].
100 belongs to range [100, 200].
150 belongs to range [100, 200].

Logical NOT operator (!)

The logical NOT operator is used to return opposite boolean result. Consider the example below:

function range_func(x){
  //! operator is used to return
  //true when x <= 100
  if(!(x >= 100))
    return x + " is less than 100.<br>";
  else
    return x + " is greater than or equal to 100.<br>";
}

var txt;
txt = range_func(50);
txt = txt + range_func(100);
txt = txt + range_func(150);

The output (value of txt) after running above script will be:

50 is less than 100.
100 is greater than or equal to 100.
150 is greater than or equal to 100.

❮ JavaScript - Operators