Branch structure / cyclic structure

A, if statements

　　Example 1:

// full Save 30 15 
var . Price = 35 ;
 IF (. Price> 30 ) { 
    . Price =. Price - 15 ; 
} 
the console.log ( 'should pay' + price); 
Results: 20

　　Example 2:

// declare variables stored Age, if the age is greater than 60, then reduction based on the original 5, the age of the final print 
var Age = 61 is ;
 IF (Age> 60 ) { 
    Age = Age - 5 ; 
} 
the console.log (Age) 
Results: 56

　　Example 3:

// declare two variables were stored username and password, if a user name is root, and the password is 123456, print successful login; 
var username = 'root' ;
 var password = '123456' ;
 IF (username = 'root' && password = '123456' ) { 
    the console.log ( 'Success' ); 
}

// writing logic short
(username = 'root' && password = '123456') && console.log ( 'success')

Result: success

　　Example 4:

// If the age is not less than 18 years old, print "adult", otherwise print "minor" 
// Note: If the statement after if only one row, it can omit the braces 
var Age = 21 ;
 if (Age> = 18 is ) { 
    the console.log ( 'adult' ); 
} 
results: adults

　　

// if the conditional expression statement, some value defaults to false
0 null NaN underdined

 

Two, if_else statement

　　Example 1:

// If the cope 27, the balance enough, successful payment, or Tip: insufficient funds, please recharge 
var Money = 50 ;
 IF (Money> = 27 ) { 
    the console.log ( 'successful payment' ); 
} the else { 
    the console.log ( 'insufficient funds, please recharge!' ); 
} 
result: successful payment

　　Example 2:

// cope 
var MONEY1 = 27 ;
 // balance 
var money2 = 25 ;
 IF (money2> = MONEY1) { 
    the console.log ( 'successful payment' ); 
} the else { 
    the console.log ( 'insufficient funds, please recharge!' ) ; 
} 
result: the balance is insufficient, please recharge!

　　Example 3:

// declare personalized signature, if there is content, print, or print "This guy is lazy" 
var Signature = '' ;
 IF (Signature == '' ) { 
    console.log ( 'This guy is lazy' ); 
} the else { 
    Console, log (Signature); 
}