'+' operator has many uses including addition, concatenation, and most importantly type conversion. Generally, we use '+' operator for addition and at some times for concatenation. It also has a lot of use in type conversion. It is very easy to convert a string into a number.
Example
<html>
<body>
<script>
var num = "23";
int = +num;
document.write(int);
document.write("</br>");
document.write(typeof int);
</script>
</body>
</html>output
23 number
Not only type-conversion, this operator is also used to convert booleans to numbers. It changes the boolean values such as true or false to 1 and 0 respectively.
Example
<html>
<body>
<script>
document.write(+true);
document.write("</br>");
document.write(+false);
</script>
</body>
</html>output
1 0