Ternary Mistery

The termary operator takes 3 operands.

They are the condition, the true expression and the false expression. The entire thing returns a value, but it is not a complete statement in itself, no more than "count < 8" would be.

The expression operands are not intended to be statements, though statements can be part of an expression. That's why your first example works, you enclosed your statements in an IIFE, which is an expression. But the second example doesn't work because grouping statements in braces still counts as a statement, not an expression.

But both of these are examples of very bad programming practices that should be avoided. Termaries should not be used to control execution flow. Even it if works, it can make the code extremely difficult to understand when read later.

Ternaries can be thought of like this.

(CONDITION) ? IF_TRUE_DO_THIS : OTHERWISE_DO_THIS;

Example

var i = 5;
function check(){
    return ((i > 3) ? 'Higher' : 'Lower');
}
check();

Would return Higher since i is greater than 3.

The reason (true)?((function(){console.log("AHH!");console.log("Oooh!");})()):"" works is the double parens at the end tell it to run the function console logging the result since true is being returned from the condition.

The reason the second one doesn't work is the {} are telling it to return a object in this case.

var test = (true) ? {} : "";
typeof test

will return "object"

var test = (true) ? { console.log('AHH!') } : "";

will error since this is not a valid object.

Wrapping things in {} works in ES6 to group things.

Example: (enter this in your console)

{
    console.log("AHH!");
    console.log("Oooh!");
}

You just can't return that from a ternary operator. Normally it's used to return a value not a entire function or a object.

Hope this helps some.