rspec/rules/S3402/javascript/rule.adoc

Use a ``+`` with two numbers and you'll get addition. But use it with a string and anything else, and you'll get concatenation. This could be confusing, especially if it's not obvious that one of the operands is a string. It is recommended to explicitly convert the non-string component to make it easier to understand to future maintainers.


This rule raises an issue when ``+`` is used with a string and a non-string.


== Noncompliant Code Example

----
function foo() {
  let x = 5 + 8;  // okay
  let z = "8"
  return x + z;  // Noncompliant; yields string "138"
}
----


== Compliant Solution

----
function foo() {
  let x = 5 + 8;
  let z = "8"
  return x + Number(z);
}
----