DevGrok

There isn't support for  async iterators ( for await...of ) in Node.js v8.9 which is AWS Lambda's runtime. It's shame, as it’s a great feature that allows you to iterate over an iterable that returns as result asynchronously, i.e. retrieving another page from a database, using a compact for loop that feels synchronous but under the covers is actually done asynchronously. Which means, if you want to use a library that written specifically to use it (e.g.  Amazon DynamoDB QueryPaginator ), you have to use an even more verbose syntax. However with a bit of re-purposing you can use a generator function that returns a Promise and if you await each promise given in the loop it will behave like an async iterator.

I've been playing around with using <template> tags  and how well they work with the current Web Component ( Custom Elements ) polyfills. My main motivation for going for Web Components instead of something like React or Angular is that I'm currently developing a chrome extension. I wanted the code base to be as small so that it didn't slow down devtools and increase the frequency of hands. Plus I think it's going to be the natural progression from the current React/Angular/etc components - especially with HTTP 2.0's server push of dependant files removing the need for tools like webpack by allow all dependant files to be automatically sent in response to one request. I immediately hit problems using custom elements in a chrome extension as they're disabled by default. So in order to use them I had to forcefully polyfill the existing API, it took a bit of fiddling  but now works with both libraries I looked at. Next, using template tags an import li...

Node.js uses async functions extensively, as it based around non-blocking I/O. Each function takes a callback function parameter, which can result in some messy, deeply nested callback functions if you have to call a bunch of async functions in sequence. Promises make these callbacks a lot cleaner. ES6 (or ES2016)  Promise s are a great way of chaining together asynchronous functions so that they read like a series of synchronous statements. There's already some great posts on Promises, 2ality has a good intro to async then detail of the api , so I won't rehash that article. However, after starting to use them for cases more complicated than most examples, it easy to make a few mistaken assumptions or make things difficult for yourself. So here is a more complicated example showing a pattern I like to follow. In this example, I'll use the new Javascript Fetch API , which is an API that returns a Promise, allowing you to make async HTTP calls without having to muck a...

I’ve been recently working heavily on JavaScript based applications in both Node.js and a Chrome extension. After working mostly on Java, I thought I’d share the syntax, conventions and the new features of ECMAScript 5.1 and parts of the still pending version, ES6 /ECMAScript 2015, that I’ve come across. Comparisons Operators == equal to === equal value and equal type != not equal !== not equal value or not equal type I saw something else I thought was a fancy notation: if (!!something) //which is not a special operator, it just converts it to boolean, i.e a double not. (!!something) === (!(!something)) //this would only be useful if you want to set a boolean to something truthy, i.e. var a = "somevalue"; var asBoolean = !!"somevalue"; Object Initializer Something I had thought was not a fully adopted syntax, was being able to specify the getter / setter functions in the initializer. (MDN Object initializer ) var o = { func1: function (p1, p2) {}, ge...

In the latest version of Safari (WebKit) they have removed some deprecated javascript API & tags which can cause problems with older code. This is my attempt to keep track of them so I can search through the code and change it to use a newer method. Here is a list of what works in Firefox 3 or Internet Explorer but not Safari: document.[form name] where [form name] matches the element <form name='[form name]'> Replacement: Use document.getElementById() instead document.embeds Replacement: Use document.getElementById() instead Form element's id defaulted to their name Replacement: Manually specify the id <applet> tag Replacement: <object> tag That's it for the moment but I'll keep updating the list as I find them.