if/elseNN 2 IE 3 ECMA 1  

  

This is a conditional statement that provides two execution paths depending on the result of the condition. You can nest another if or if/else statement inside either path of the if/else statement.

 
Example
  
var theMonth = myDateObj.getMonth( );
if (theMonth == 1) {
    monLength = calcLeapMonthLength( );
} else {
    monLength = calcMonthLength(theMonth);
}