Javascript 速记 if-else 并返回

Question

Can the javascript shorthand for if-else return out of a function? If so how would this work.

eg. I have this:

if(boolean){
 return;
}

and I would like to write it as this:

(value)? return;

Chrome complains that return is unexpected. Is there anyway to write something like this so that it is valid?

Answer 1

No, you can't do that unless you return a value. For example if your function had to return a value you could have written:

return boolean ? 'foo' : 'bar';

But you cannot stop the execution of the function by returning void using the conditional operator.

Answer 2

If you intend to return from the function at this point in its execution regardless of whether the test evaluates true or false, you can use,

return (value) ? 1 : 2;

But if you merely wish to return early when a test evaluates true (for instance, as a sanity-check to prevent execution when parameters are invalid), the shortest you can make it is:

if (boolean) return;

Answer 3

if(boolean) return;

单行，可读，完全有效;

Answer 4

I know it's an old question but I want to add that there is a non-standard way to return out of a function in shorthand if-else, and that is performing Immediately Invoked Function Expression ( IIFE ):

function outOfFunction(boolean){

    return (boolean)?(()=>{return true;})():(()=>{return false;})();

}

console.log(outOfFunction(true));
console.log(outOfFunction(false));

And if we want to be out of the function or continue with other task:

    function shorthandExampleJustTrue(boolean){

        var someVar = "I'm out";        

        return (boolean)?(()=>{return true;})():(()=>{

          console.log("here my code ");

          console.log(someVar);

          return "anythig else";


        })();
    }

console.log(shorthandExampleJustTrue(true));
console.log(shorthandExampleJustTrue(false));

When we use arrow functions we are able to access to variables out of the immediate function context.

Answer 5

if I'm not mistaken you're talking about this right? a short-hand.

 return (if the value here is true then ->) && false

example:

const isGood = true && "yeah";
console.log(isGood) //yeah

Use this as your short hand if the value is true then it will return false; using the && operator is better

Answer 6

You want to do a ternary operator

which is this:

(bool) ? ifTrue : ifFalse;

Please note: you cannot omit the else portion of a ternary operator.

http://en.wikipedia.org/wiki/Ternary_operation

Answer 7

The conditional "ternary operator" ( condition ? expression to evaluate when true : expression to evaluate when false ) is often used for simple conditional variable assignment.

if you need :

if( x > 0) {
   a = 10;
}else{
   a = 30;
}

you can write:

a = (x>0)? 10 : 30; 

You can think of it like a simple function, which takes 3 parameters (p1, p2, p3), if p1 is true it returns p2 and if p1 is false then it returns p3.

(p1)? p2 : p3;

And just like such a function, there's no way for it to cause the parent function to return based on the condition. It is not therefore a shorthand for if/else.