var num = "1";
num = num+1; //Gives "11"
but
var num = "1";
num++; //Gives 2.
Why?
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4 Answers
Because the + operator is also used for string concatenation.
var num = "1";
// The 1 is converted to a string then concatenated with "1" to make "11".
num = num+1;
Javascript is a weakly typed language, so it's more lenient about type conversions.
The ++ operator used in your case is the postfix increment operator which only operates on numbers, so it acts as you expect:
var num = "1";
// num is converted to a number then incremented.
num++;
To give a hint that addition should take place, subtract by zero:
var num = "1";
// Subtraction operates only on numbers, so it forces num to be converted to an
// actual number so we can properly add 1 to it
num = (num - 0) + 1;
Or use the unary + operator:
var num = "1";
// The unary + operator also forces num to be converted to an actual number
num = (+num) + 1;
Comments
Because ++ is an numeric operation, so num is cast from string, then the operation takes place.
The + however can be both for numeric operands (add), as well as string operands (concatenation). So 1 is cast to string, then concatenated with 1, which gives 11.
Comments
var num = "1";
num = num+1; //Gives "11"
First one is, + operator is string concatenation. So you get the concatenation result.
var num = "1";
num++; //Gives 2.
Second one is, ++ operator is post increment operator. So you get the added result.
If you wish to change the + operator for addition. Use like this
var num = "1";
num = parseInt(num)+1; //Gives "2"
The parseInt() function parses a string and returns an integer. So it return the integer value.
