Why does adding two arrays in JavaScript using the operator result in a string instead of a new array?

Why Does [1,2] [3,4] Result in "1,23,4" in JavaScript?

When attempting to add the elements of two arrays, such as [1,2] and [3,4], using the operator in JavaScript, you may encounter an unexpected result: "1,23,4". This result occurs because the operator behaves differently with arrays compared to other data types.

The Role of the Operator

The operator in JavaScript has several different uses depending on the types of operands involved. When used with numbers, it performs addition. With strings, it concatenates them. However, when used with arrays, it does not perform a mathematical or concatenation operation.

JavaScript's Type Coercion

Instead of performing a defined operation for arrays, JavaScript coerces, or converts, arrays into strings before performing the operation. This is known as type coercion. In the case of [1,2] [3,4], the arrays are converted to the strings "1,2" and "3,4" before the concatenation operation.

The Result

After type coercion, the operator simply concatenates the two strings, resulting in "1,23,4". This is because there is no comma separator within the original arrays, and JavaScript does not add any spacing when concatenating strings.

Additional Notes

It's important to note that the operator does not work in the same way for all objects in JavaScript. For instance, with Number and Boolean objects, it performs addition operations. However, with custom objects, the behavior may vary depending on the implementation of the valueOf and toString methods.

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