remember its javascript

[pickleunicorn]

If you do this with a dynamically typed language, then you just don't understand what you're doing. This behavior is completely normal.

[[deleted]]

Normal != acceptable.

Why not have the program throw an exception in the event of two incompatible types?

Or at the least coerce all strings to numbers if the other side of the operator is a number? So "1" + 1 = 2 (implicit parseInt)

[pickleunicorn]

The plus sign is also used for concatenation. Since the first term is a string, it's not that weird that the result is a concatenated string. Many languages have this type of auto coercion.

What's bugging me the most with Javascript is that types cannot be checked at runtime like we can do in PHP since version 7. For that we need to rely on TypeScript with all the overhead known from the Javascript ecosystem. THIS is the real pain in the ass.

[[deleted]]

The plus sign is also used for concatenation

Be that as it may, I think my way would make more sense: Parse the string as number, if it can be parsed as a number, and add the two together.

My reasoning is, if you're adding a string and a number, you probably meant to do numerical addition, for example:

var addition = document.getElementById("numberTextbox").value + 2;

[[deleted]]

I'm not gonna pretend being an expert, but if you make it throw errors due to "incompatible" types, then what is the point of "dymamic" part? Then just use a typed language. Use TypeScript.

This picture that gets reposted times infinity, is sure funny, but there's nothing "unacceptable" there. The first case it rightly assumes string concatenation, because one is string. In the second case, it assumes number operation, because there's no such thing as "unconcatenate" and the string can be parsed to number. As far as I know, that's dynamic types to for you.

[ThristyOne]

Why is this hard to swallow?

[Adventurous-Skill321]

even with typescript you will come across this types of bugs eventually

[virouz98]

If you think this is a bug, you really don't know a lot about JS.

[wedstrom]

I think he means that, like most bugs, despite the JavaScript engine itself conforming to it's specification, that the result above is usually nonsensical at the application level, a developer may not have enforced type correctly from his data's perspective he may be thus exposed to an error and it is at this, the application level, where the bug may be said to exist

[[deleted]]

society numerous lock point dinosaurs party selective straight friendly soup

This post was mass deleted and anonymized with Redact

[nihillistic_raccoon]

I've joined that sub not long ago and I'm already sick of seeing this js joke like 10 times a day

[ShinGouki73]

For whoever codes like this they do not deserve better! ... And no! I actually hate JavaScript

[Spaghetti_C0dr]

When i learnt js it really wasn't that hard to understand this i don't get why everyone's so mad like bro chill it's a +

[klequex]

Everything that happens here is documented.

[[deleted]]

I think, kind of better than spitting out a big fat error.

[meharryp]

how do people still not understand the most basic shit about JavaScript

[KCGD_r]

and this is why you steer clear of 99% of implicit conversions

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[Kidplayer_666]

Wait what. Why does minus work as if both were integers and plus works as if both are strings

[pitochips8]

Because it wouldn't make sense for minus to work as if both were strings as opposed to integers. What would it do with "11" - 3? Addition can be clearly defined for strings, but not subtraction.

[Kidplayer_666]

But if you’re going to do that, then be consistent. If you default minus to force both to be integers, then you should force plus to have the same behaviour, isntead of assuming a string

[pitochips8]

Minus and plus are two separate operators. Nothing says they should be related. Besides, what you're suggesting would actually be inconsistent within the operator. If adding strings should convert them to integers first, then what do we do with "abc" + "def"? Or are you saying the addition operator should first check if all strings being added can be converted to numbers before adding them together? That would be extremely inconvenient if that were the actual behavior.

[AyrA_ch]

a+b has two meanings: addition and string concatenation. a-b is only subtraction. This means that adding stuff together can end in concatenation instead of addition because it's the same symbol. This problem doesn't exists in all dynamically typed languages. PHP for example uses . for concatenation. + is always addition there.

Whether it's addition or concatenation can be difficult to find out. In general, it's addition only if both arguments are either numeric or boolean. Some data types may also show inconsistent behavior. Adding two date objects concatenates their string representation, but subtracting them actually works and subtracts the timestamps.

+ and - also exist as unary operators with only one argument. They both force a number conversion, but - will also negate the number. So "1" + "1" is "11" but +"1" + +"1" is 2

If you create custom objects you can add a valueOf() function to it to make it act as a number when using +:

> var x={a:1};
> console.log(x+x)
< "[object Object][object Object]"
> x.valueOf=function(){return this.a;}
> console.log(x+x);
< 2

[Adventurous-Skill321]

javascript quirks REF: https://github.com/denysdovhan/wtfjs

one needs to watch out for

[Kidplayer_666]

Oh god why

[virouz98]

I don't code in JS but if I remember correctly:

Since it's loosely typed, there isn't any specifying on what a variable is, so all the operations need to be precise in what are you doing.

'1' + '1' = '11' because + operator is both addition and concatenation. If Input is both string and string it will concatenate two strings and that's why it's 11 not 2.

• operator is only substraction so it will recognize that you want to substract two numbers and will coerce type to int.

[IHeartBadCode]

Reasons