Javascript + operator [duplicate]

Question

What is the application of the plus operator in these cases? I have seen it used in these ways but don't see how it operates.

start = +new Date;

+array[i]

+f.call(array, array[i], i)

x = +y

Answer 1

+ will implicitly cast a string / boolean value into a Number().

+"66" === 66

---

If the string cannot be converted into a Number, the value will be NaN

+"not possible" // evaluates to NaN

---

In the case of a Date() object, + will also cast the data into its numerical representation, that is the UNIX timestamp.

So, finally spoken, leading an expression with + is pretty much the same as explicitly wrapping the Number() constructor around it:

+new Date()

equals

Number( new Date() )