Page Title

Adding strings and numbers in JavaScript

String on this page refers to a number that is of type string.

Adding two numbers is as expected; just simple math.
5 + 6 = 11

Adding two strings will concatenate them, even if the strings are numbers.
"5" + "6" = 56

If one string and one number are added, the two values are concatenated. The number is added as if it were a string.
4 + "9" = 49
"4" + 9 = 49

The values are added left to right, so if two numbers are added, and then a string is added, the numbers are added first as numbers would be, and then the string is concatenated. As soon as a string is added, the answer becomes a string, and any following values are concatenated.
1 + 2 + "3" = 33
1 + "2" + 3 = 123
"1" + 2 + 3 = 123
1 + 2 + 3 + 4 + "5" + 6 + 7 = 10567

If put a plus sign in front of the string, it is converted to a number.
+"6" + 5 = 11
8 + +"9" = 17

If you subtract a string from a number, or subtract a number from a string, the string is treated as a number.
"9" - 5 = 4
12 - "6" = 6
"4" + "4" + "4" - 100 = 344

You can see more examples in the JS and console.

JS - adding numbers and strings