Why is the last operation returning 20?
console.log(2 + 2); // equals 4
console.log("2" + "2"); // equals "22"
console.log(2 + 2 - 2); // equals 2
console.log("2" + "2" - "2"); // equals 20Why is string number addition not coalescing intuitively
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2 Answers
+ and - evaluate left-to-right. When either operand is a string, the result is concatenation. When both are numbers, the result is addition.
In contrast, - will always coerce both sides to numbers.
'2' + '2' - '2'
does
// left-to-right
('2' + '2') - '2'
// both sides are strings, so concatenate
'22' - '2'
// operator is -, so coerce both sides to numbers
22 - 2
20
The signs + and - work very differently in string concatenation. The + operator gives direct concatenation instructions on strings whereas the - operator tries to coerce the types and perform the mathematical function.
console.log("2" + "2");
console.log(typeof ("2" + "2"));
console.log("2" - "2");
console.log(typeof("2" - "2"));Related