Operator + is a unary operator which converts value to number. Below I prepared a table with corresponding results of using this operator for different values.
+-----------------------------+-----------+
| Value | + (Value) |
+-----------------------------+-----------+
| 1 | 1 |
| '-1' | -1 |
| '3.14' | 3.14 |
| '3' | 3 |
| '0xAA' | 170 |
| true | 1 |
| false | 0 |
| null | 0 |
| 'Infinity' | Infinity |
| 'infinity' | NaN |
| '10a' | NaN |
| undefined | Nan |
| ['Apple'] | Nan |
| function(val){ return val } | NaN |
+-----------------------------+-----------+
Operator + returns value for objects which have implemented method valueOf.
let something = {
valueOf: function () {
return 25;
}
};
console.log(+something);