why there is no condition in the if statement when we use if(err) for mongoose query?

Question

I know this might be a noob questions, but when I handle error for mongodb, why don't we put a condition like this in inside the if statement?

For example

query.findOne(function (err, kitten) {
    if (err === true) {
        console.log(err);
    } else if (!err) {
        console.log("success");
    }
}

How is if(err) equivalent to if(err===true)?

`if(err)` is not necessarily equivalent to `if(err===true)` - You need to check that in the console — Alon Eitan, Aug 30 '20 at 08:21
Does this answer your question? [Understanding JavaScript Truthy and Falsy](https://stackoverflow.com/questions/35642809/understanding-javascript-truthy-and-falsy) — tevemadar, Aug 30 '20 at 08:22
I am using the mongoose query for example query.findOne(function (err, kitten) { — Eric, Aug 30 '20 at 08:23
because if (true) is the same as saying if (err===true) when err is true. As err === true also evaluates to true. :P — Muhammad Kamran, Aug 30 '20 at 08:25

score 1 · Accepted Answer · answered Aug 30 '20 at 08:24

1

If err is a boolean variable, and is set to True, then you do not need to write if(err===True) because it is the same as writing if(True) (because err is true). In contrast, if you want to check if the condition is False, then you write if(!err). If err is True, then !err= !True = False

answered Aug 30 '20 at 08:24

LoukasPap

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This does answer my question, but I have something that I want to dig in. What if err is not an boolean value, for example when I use the mongoose query. I am not sure what kind of variable is the err, but I don't think its simply just a boolean variable since when I console log it, it shows more. And for this case, how would I understand this? – Eric Aug 30 '20 at 08:28
What does it show you, when you print it on console? – LoukasPap Aug 30 '20 at 09:15

why there is no condition in the if statement when we use if(err) for mongoose query?

1 Answers1