One liner that returns a value if evaluation is truthy and breaks if evaluation falsy?

Question

Here is a piece of code I have in several places in my code:

req = this.getActiveRequestById(message.trans_id);
if (!req) {
    break;
}

How can I rewrite this as a one-liner?

EDIT I want to clarify that I need to store the return value in req for later use.

`if (!this.getActiveRequestById(message.trans_id)) break;`? What's the problem here? — nick zoum, Feb 13 '19 at 12:03
Possible duplicate of [How do you use the ? : (conditional) operator in JavaScript?](https://stackoverflow.com/questions/6259982/how-do-you-use-the-conditional-operator-in-javascript) — Liam, Feb 13 '19 at 12:04
*How can I rewrite this as a one-liner?* I would also question why here? why is this is a problem? — Liam, Feb 13 '19 at 12:05
@user1283776 And else you need to fall-through? If you are asking how to simplify your code and avoid duplicating parts, please post the whole code so that we can suggest an appropriate abstraction. — Bergi, Feb 13 '19 at 12:19
Thanks @Bergi: I'll try to keep your advise in mind for the future — user1283776, Feb 13 '19 at 12:54

Mosè Raguzzini · Accepted Answer · 2019-02-13T12:12:06.730

3

Remove var assignment and apply the condition directly to the value:

if (!this.getActiveRequestById(message.trans_id)) break;

I would not suggest it but if you need to set a variable in a one liner if condition it should work:

 if (!(req = this.getActiveRequestById(message.trans_id))) break;

Notice that it generates confusion between comparison and assignment.

edited Feb 13 '19 at 12:12

answered Feb 13 '19 at 12:04

Mosè Raguzzini

score 1 · Answer 2 · answered Feb 13 '19 at 12:09

1

if (!(reg = this.getActiveRequestById(message.trans_id))) break;

answered Feb 13 '19 at 12:09

2 Answers2