Creates a new UserAgentBag by parsing string as a User-Agent per RFC7231. string must have a length of 256 characters or less (this limit may be configurable in the future). If there are any errors in parsing, the bag will be empty.

`js
const validBag = new UserAgentBag("Foo/1.2");
validBag.get("Foo");
// => '1.2'

const invalidStringBag = new UserAgentBag(
"Foo/1.2 IsInvalidBecauseVersionIsMissing/"
);
invalidStringBag.get("Foo");
// => undefined
`

Creates a new UserAgentBag from iterable. Elements of iterable are key-value pairs.

`js
const bagFromEntries = new UserAgentBag([
["Foo", "1.2"],
["Bar", null],
]);
bagFromEntries.toString();
// => 'Foo/1.2 Bar'

const myMap = new Map();
myMap.set("Baz", "5");
myMap.set("Qux", "6");
const bagFromMap = new UserAgentBag(myMap);
bagFromMap.toString();
// => 'Baz/5 Qux/6'
`

Returns an iterable yielding each of the product-version pairs in the bag. Like Map.prototype.entries.

`js
const bag = new UserAgentBag("Foo/1.2 Bar Baz/3.4");

for (const [product, version] of bag.entries()) {
console.log(product + " version " + version);
}
// Logs:
// Foo version 1.2
// Bar version null
// Baz version 3.4
`

Returns the version of the product. If product is in the bag multiple times, only the first value is returned. If no version is specified, null is returned. If the product is missing from the bag, undefined is returned.

`js
const bag = new UserAgentBag("Foo/1.2 Bar/4.5 Bar/6.7 Baz");

bag.get("Foo");
// => '1.2'

bag.get("Bar");
// => '4.5'

bag.get("Baz");
// => null

bag.get("missing");
// => undefined

bag.get("foo");
// => undefined
`

Returns all specified versions of the product as an array. null represents the absence of a version. If the product is missing from the bag, the empty array is returned.

`js
const bag = new UserAgentBag("Foo/1.2 Bar/4.5 Bar/null");

bag.getAll("Foo");
// => ['1.2']

bag.getAll("Bar");
// => ['4.5', null]

bag.get("missing");
// => []
`

Returns true if product is in the bag, false otherwise.

`js
const bag = new UserAgentBag("Foo/1.2 Bar");

bag.has("Foo");
// => true

bag.has("Bar");
// => true

bag.has("missing");
// => false
`

`js
const bag = new UserAgentBag("Foo/1.2 (ignored comment) Bar/3 Bar/4");
bag.size();
// => 3
`

`js
const bag = new UserAgentBag([
["Foo", "1.2"],
["Bar", null],
]);
bag.toString();
// => 'Foo/1.2 Bar'
``