Usage of rest parameter and spread operator in javascript

Question

What\'s the usage of rest parameter that will be added in ECMAScript 6?

For example, in ECMAScript 5 you can do the following to get an array of parameters starting

Answer 1

I think the main differences in rest parameter are:

• Arguments in ECMA5 arguments is like array not an array, so array normal methods is not available, but in ECMA6 arguments is an array.
• I think building items array in ECMA5 code example will make the code a little slower because new array is instantiated.