Node.js Tutorial - Node.js Booleans

• « Previous
• Next »

The boolean type Values in JavaScript can either be true or false.

Two literals are defined for boolean values: true and false.

We can convert values to boolean with the Boolean function, and the language converts everything to boolean when needed, according to the following rules:

false, 0 , empty strings "", NaN , null , and undefined all evaluate to false .

All other values evaluate to true .

Example

console.log(0 == false);/*from   ww  w. j  a va  2 s .com*/
console.log("" == false);
if(null){
}else{
   console.log("false");
}
if(undefined){
}else{
   console.log("false");
}
if(NaN){
}else{
   console.log("false");
}

The code above generates the following result.

Example 2

We can assign these to variables and apply boolean operations to them.

var myData = true; 
console.log(myData); // true 
/*from   w  w  w  .  java  2s .  co  m*/
// Boolean operations (&&, ||, !) work as expected: 
console.log(true && true); // true 
console.log(true && false); // false 
console.log(true || false); // true 
console.log(false || false); // false 
console.log(!true); // false 
console.log(!false); // true 

The code above generates the following result.

• Next »
• « Previous