ES6 Generators

(and maybe a little arguments + destructuring, too)

Generators - Function or Object?

  • Generator functions return the generator object
  • Generator object conforms to iterable and iterator protocols

Generator Function

  • Special type of function that can pause & resume execution
  • Automatically generates an iterator
  • Utilizes "yield" keyword to indicate the value returned for each call to next()

Wait - what's an iterator?

  • iterators return an object with a next() method on it
  • if wanted, you could manually iterate like above

why iterate manually...for-of handles this for us!

You can create custom iterators

OK - Back to Generator Functions

  • Special type of function that can pause & resume execution
  • Automatically generates an iterator
  • Utilizes "yield" keyword to indicate the value returned for each call to next()
  • yield pauses execution inside generator function
  • for-of iteration automatically calls "next()" on the generator (until no more values are yielded)

What the Generator Function Returns

Manually Calling Next

Generators are Lazy

Generators ♡ Destructuring

Generators ♡ ...Spread

Generators ♡ Other Generators

Generators ♡ Custom Iterables

A Sidebar on ES6 Spread

  • new operator full of chocolatey goodness :-)
  • spread an expression over multiple arguments
  • can work with any iterable!

Spreading Arguments

Iterables all Around!

Since We Brought Up Arguments...

This is confusing:

configureServer( "196.168.0.1", "8787", true, true );

But, why?

This is better:

configureServer({
    server: "196.168.0.1",
    port: "8787",
    enableCache: true,
    logFailures: true
});

But this is verbose

function configureServer( options ) {
    options.port = options.port || "8888";
    // both setting defaults and having to
    // use dot notation off of options
}

ES6 Destructuring FTW

What About Default Params?

What About Required Params?

Aaaand we're done

ES6 Generators

By Jim Cowart

ES6 Generators

Informal LeanKit web team training slides

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