JavaScript String Manager

Question

Why in JavaScript
"11" + 1 = "111"

And

"11" - 1 = 10

Answer 1

"11"- 1 = 10

JavaScript sees that "11" is a string and it sees something is being subtracted from it. It says to itself, “Huh. Something is being subtracted from a string. Does that make sense to me? What do I do when something’s subtracted from a string?” It doesn’t have a rule for that!

So it says, “Well, that second argument, the 1, is a number. What if I turn the first argument, the "11", into a number. Can I do that?” It turns out that, yes, it can turn the string "11"into a number.

So then it asks, “Does subtracting one number from another make sense? Do I have a rule for subtracting one number from another?” It turns out that, yes, it does know how to subtract one number from another. So it converts the string, "11", to the number, 11, subtracts 1 from it, and displays the result, 10.

Answer 2

Use parseInt(string).

Answer 3

Filipe Cláudio I don't ask how to solve but I asked why
I know JavaScript

Answer 4

let a = [];
a[0] = 10;
console.log(a+1); // result 101

let b = [];
b[0] = 10;
console.log(parseInt(b)+1) // result 11

Answer 5

Ok sorry, I just wanted to help

Answer 6

Anton Böhler There Must be a reason

Answer 7

It takes place due to coercion...

In first case the number 1 is coerced to string and hence displayed as 111

Meanwhile the subtraction operator coerces the 11 to number so 10

https://hackernoon.com/understanding-js-coercion-ff5684475bfc

Answer 8

"11"+1 will convert 1 to string to be "111"

"11"-1 will convert 11 to number to be 10

And with mult and div same sub...

Answer 9

you've made a little fault, its:
"11" + 1 = "111"
"11" - 1 = 10

Answer 10

Anton Böhler No

Answer 11

Qudusayo probably to avoid runtime errors and also to shorten code 🤷‍♂️

Answer 12

Qudusayo it's just the way JavaScript handles such operations. 🤷‍♂️

Answer 13

Good reads for inquiring minds

https://medium.com/@julianknodt/javascript-operator-overloading-e1ebd2344b78,
https://medium.com/codezillas/let-me-coerce-you-into-liking-javascripts-dynamic-typing-system-3cd22c19cb64

Answer 14

if there's string data type,
then + operator in javascript is to concat string and the closest number data type.

Answer 15

The simplest and often used way to cast a number to a string is by using the + operator.

14 + "" // "14"
Whenever you are using “+” or “-” the values that you are adding or subtracting must be of the same type. Now in the above example they obviously are not. So what will happen is that JS will try to even them out — in this case cast our number to a string and then add them together. In other words every “+” expression that involves a string will result in a string.

42 + "0" // "420"
We can concat strings using “+”, but what will happen if we use “-”? It can be used only on numbers, so once again, JS will cast the values to be of the same type — this time numbers.

"42" - 7 // 35
"42" - 0 // 42
"42" - "9" // 33
Okay that’s not that hard, but there is always a catch. Let’s try adding two arrays together and see what happens:

["alex", "sam"] + ["jon", "mary"] // "alex,samjon,mary"
Wait, what just happened? Now, whenever you use the “+” operator, the values will concatenate if one is already a string or they