if..else if .. else语句的一行

Question

I tried to write one line if..elseif..else statement but it always goes in else if .

 var x = "192.168.1.1"; x = x == ("google.com") ? ("true google.com") : (("yahoo.com") ? ("true yahoo.com") : ("192.168.1.1")); console.log(x); 

Is there something I am missing? Why does it always go in else if ?

Answer 1

You missed the x == (""yahoo.com"") statement

 var x = "192.168.1.1"; x = (x == "google.com") ? "true google.com" : (x == "yahoo.com") ? "true yahoo.com" : "192.168.1.1"; // --------------------------------------------^^^^^^^^^^^^^^^^------------------------------------ console.log(x); 

But it will be more readable with if - else if - else statements. Don't make your code concise if it will decrease the readability.

Answer 2

This does not answer the question

Why does it always go in else if ?

but it could help with

Is there something I am missing?

Yes, you mis some clarity for further use and a clear pattern, how to get for a given string another string.

You could use an object, which is easy to maintain for the keyed values.

 values = { "google.com": "true google.com", "yahoo.com": "true yahoo.com", default : "192.168.1.1" }; 

The call works with a default operator || (logical OR):

x = values[x] || values.default;

 var x = "192.168.1.1", values = { "google.com": "true google.com", "yahoo.com": "true yahoo.com", default : "192.168.1.1" }; x = values[x] || values.default; console.log(x); 

Answer 3

Your ternary operation

x = x == ("google.com") ? ("true google.com") : (("yahoo.com") ? ("true yahoo.com") : ("192.168.1.1"));

can be thought of as if-else if-else block as follows:

if(x == ("google.com")) {
   x = "true google.com";
}
else {
   if("yahoo.com") {
       x = "true yahoo.com"; //Always true since it is a non-empty string
   }
   else {
       x = "192.168.1.1"
   }
}

So since you are initializing x to "192.168.1.1", it obviously is not equal to the the string specified ("google.com") in the first condition ( if block). So it moves on to the else block and evaluates the if condition inside the else block. This if block in turn only checks if a string literal "yahoo.com" is empty or not. Since it is not empty, the condition is satisfied.

For your purpose, you need to change that from if("yahoo.com") to x == if("yahoo.com") . However, once you make this change, it will always go to the else block because the first two conditions will never satisfy.