How does adding String with Integer work in JavaScript? [duplicate]

Question

The following code gives weird results:

console.log("" + 1 + 10 + 2 - 5 + "8");

I've tried inputting various different values to work it out but I cannot understand what's going on under the hood.

Answer 1

"" + 1          === "1" "1" + 10        === "110" "110" + 2       === "1102" "1102" - 5      === 1097 1097 + "8"      === "10978" 

In JavaScript, the + operator is used for both numeric addition and string concatenation. When you "add" a number to a string the interpreter converts your number to a string and concatenates both together.

When you use the - operator, however, the string is converted back into a number so that numeric subtraction may occur.

When you then "add" a string "8", string concatenation occurs again. The number 1097 is converted into the string "1097", and then joined with "8".

Answer 2

string + number = concatenated string

number + number = the sum of both numbers

string - number = the difference between (coerced string) and the number

explanation:

If one or both operands is string, then the plus is considered as string concatenation operator rather than adding numbers.

the minus operator always try to convert both operands to numbers.

so:

"" + 1 + 10 + 2 = (string) "1102"     "1102" - 5      = (number)  1097 1097 + "8"      = (string) "10798"