bugs in {#spread-operator} section

[marzelin]

function add(...values) {

... token used in a parameter list is called rest parameter

---

var values = Array.prototype.splice.call(arguments, [1])

should be

var values = Array.prototype.slice.call(arguments),

for following reasons:

• arguments object shouldn't be modified (splice mutates an object, slice doesn't)
• call expects a list of arguments, not an array (for arrays there's apply method)
• add function should add every number given in arguments (slice(0) which equate to slice())