What is Addition Operator (+) in JavaScript?

The addition operator (+) in JavaScript is used to add two numeric operands together. It performs mathematical addition and returns the sum of the values.

Syntax

result = operand1 + operand2;

Example

You can try to run the following code to work with the addition operator:

<html>
   <body>
      <script>
         var a = 33;
         var b = 10;

         document.write("a + b = ");
         result = a + b;
         document.write(result);
      </script>
   </body>
</html>
a + b = 43

String Concatenation vs Numeric Addition

The + operator also performs string concatenation when used with strings:

<html>
   <body>
      <script>
         var num1 = 5;
         var num2 = 10;
         var str1 = "Hello ";
         var str2 = "World";

         document.write("Numeric addition: " + (num1 + num2) + "<br>");
         document.write("String concatenation: " + str1 + str2);
      </script>
   </body>
</html>
Numeric addition: 15
String concatenation: Hello World

Key Points

  • With numbers: performs mathematical addition
  • With strings: performs concatenation
  • Mixed types: converts numbers to strings and concatenates
  • Returns the sum for numeric operations

Conclusion

The addition operator (+) is fundamental in JavaScript for both numeric addition and string concatenation. Understanding its dual behavior with different data types is essential for effective JavaScript programming.

Updated on: 2026-03-15T21:59:05+05:30

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