Why Does JavaScript Act Differently with Plus and Minus Operators When Used with Strings and Numbers?

JavaScript's Intriguing Behavior with Plus and Minus Operators

JavaScript's handling of the plus ( ) and minus (-) operators when applied to strings and numbers has often puzzled programmers. This article will unravel the puzzle, exploring why these operators behave differently in such scenarios.

Consider the following code:

console.log("1" + 1); // Prints "11"
console.log("1" - 1); // Prints "0"

To understand why JavaScript produces these outputs, we need to delve into the nature of the operators and the data types involved.

String Concatenation with Plus ( ) Operator

When the plus ( ) operator is applied to a string, such as "1", and a number, it performs string concatenation. In this process, the number is converted to a string, and the two strings are appended together. Therefore, in the first example, "1" is concatenated with "1" to produce "11".

Number Subtraction with Minus (-) Operator

On the other hand, the minus (-) operator cannot be applied to strings directly. When a string is encountered, JavaScript attempts to convert it into a number. However, if the conversion fails, as in the second example, the result is NaN (Not-a-Number). To avoid this, JavaScript coerces the string "1" into a number, resulting in the subtraction of 1 from 1, which produces 0.

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