If condition

var age = 33; 

if (age > 18) {
    console.log("Your are an adult.");
}

if-else

var age = 15; 

if (age > 18) {
    console.log("You are an adult."); 
} else {
    console.log("You are not an adult yet.");
}

During equality test, use === for strict equality:

a = 4; 
b = "4"; 

a == b // this will result true. 
a === b // this will result false 

And and or operators are denoted by && and ||, respectively.

var age = 35; 

if (age > 18 && age < 60) {
    console.log("You are an adult but not a senior citizen."); 
}

There is a shorthand for if-else condition as well:

if (a==b) {
    console.log("Match"); 
} else {
    console.log("No match");
}

is same as:

a==b ? console.log("Match") : console.log("No match");