I had a bit of a weird result in the javascript console. I was trying to look for an alternative (more readable) version of the ternary operator, just for fun. Typing:

{ if(3===4) {5} else {6} }

Evaluates in my console to 6, but for some reason, I can not assign it to a variable, so running:

let a = { if(3===4) {5} else {6} }

Does not let me store it to the variable directly. So my main question is, if this block is returning something, why can't I assign it?

I had a bit of a weird result in the javascript console. I was trying to look for an alternative (more readable) version of the ternary operator, just for fun. Typing:

{ if(3===4) {5} else {6} }

Evaluates in my console to 6, but for some reason, I can not assign it to a variable, so running:

let a = { if(3===4) {5} else {6} }

Does not let me store it to the variable directly. So my main question is, if this block is returning something, why can't I assign it?

• javascript

• 1 You can not “assign” an if statement to a variable, that makes no sense to begin with. If you want to do it like this, then you have to assign values to a inside the if and else branch code blocks. – C3roe Commented May 14, 2018 at 12:21
• @CBroe Whether or not it "makes sense" is language-dependent, e.g., we do it in Ruby all the time. – Dave Newton Commented May 14, 2018 at 12:31
• Yes thats why I was asking, this is pretty mon in some other languages. – user2662833 Commented May 14, 2018 at 12:52
• The ternary operator (?:) is an operator, if is a statement. Operators and statements are different concepts, with different purposes in a program. They cannot be interchanged. – axiac Commented May 14, 2018 at 12:59
• Curious if you want to assign a function to a variable? This link does that and invokes later stackoverflow./questions/36664097/… – user4573148 Commented May 17, 2018 at 2:42

4 Answers 4

The fact that blocks (and other statements) return values isn't accessible to your code. Consoles can see the result, and it exists at a language specification level, but not in your code.

Your options are the conditional operator¹ (which is quite readable when you're used to it, but you've said you're looking for alternatives to it) or the if/else assigning to a in both parts:

let a;
if (3 === 4) {
    a = 5;
} else {
    a = 6;
}

Or you could use an inline function (IIFE):

let a = (() => { if (3 === 4} return 5 else return 6; })();

There is also a proposal being floated for "do expressions", which would look like this:

// Currently a proposal, not implemented in engines yet
let a = do { if (3 === 4) 5; else 6; };

That proposal is at Stage 1 of the process, so it may or may not progress, and if it progresses it could change markedly before doing so.

¹ Although you see "the ternary operator" a lot, the proper name is the conditional operator. It is a ternary operator (an operator accepting three operands), and currently JavaScript's only ternary operator, but that could change someday. :-)

Use ternary operator, because you can't assign if statement:

let a = 3 === 4 ? 5 : 6;

The reason this doesn't work is because if is, as you pointed out, a statement. An assignment requires an expression holding a value to be assigned. A statement doesn't (per se) have a value--it simply performs some side-effect instead.

What you can use if you want to assign a value conditionally is the ternary conditional operator, which is an expression:

let a = (3 === 4 ? 5 : 6)

At this point you're probably wondering, why does the console print a value if a statement merely performs side-effects? This is because statements have a pletion value, which for an if statement is the pletion value of the corresponding branch, and for an expression statement (which is what the 5 and 6 inside the blocks are), is whatever the expression evaluates to. This is mainly useful for when you want to evaluate an expression in the console and see what it produces, without having to issue a console.log() each time you do.

It's not returning anything. if is not an expression, it's a statement; it has no value.

The point of the ternary operator was to provide a more readable version of this:

let a;
if (condition) {
    a = 1;
}
else {
    a = 2;
}