javascript ... operator

//The operator ... is part of the array destructuring.
//It's used to extract info from arrays to single variables.
//The operator ... means "the rest of the array".
var [head, ...tail] = ["Hello", "I" , "am", "Sarah"];
console.log(head);//"Hello"
console.log(tail);//["I", "am", "Sarah"]

//It can be used to pass an array as a list of function arguments
let a = [2,3,4];
Math.max(a) //--> NaN
Math.max(...a) //--> 4/* JavaScript shorthand -=
-= is shorthand to subtract something from a
variable and store the result as that same variable.
*/

// The standard syntax:
var myVar = 5; 
console.log(myVar) // 5
var myVar = myVar - 3;
console.log(myVar) // 2

// The shorthand:
var myVar = 5;
console.log(myVar) // 5
var myVar -= 3;
console.log(myVar) // 2
Operator	Example	Same As
=	x = y	x = y
+=	x += y	x = x + y
-=	x -= y	x = x - y
*=	x *= y	x = x * y
/=	x /= y	x = x / y
%=	x %= y	x = x % y
**=	x **= y	x = x ** y