- Early Days
- Created by Brendan Eich at Netscape in 10 days in 1995
- Was not a highly respected programming language for about 10 years
- Based on functional languages with some object-oriented patterns; is a multi-paradigm language
- Applications like Google Maps and Gmail were where JavaScript gained popularity
- Standards
- The standard for JavaScript implementations is called ECMAScript
- Given that there are several competing JavaScript engines, the European Computer Manufacturers Association (ECMA) is responsible for standardizing JavaScript, referred to as ECMAScript
- The standard is updated yearly and the standard for that year is called ECMAScript 20xx (or ES 20xx); ES2015 or ES6.
- Browser Wars still leave us with legacy JavaScript implementations (and weirdness)
- We can use transpiling to write JavaScript according to the standard we want and convert it to code that can be used for the majority of JavaScript applications
- The standard for JavaScript implementations is called ECMAScript
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Request-Response lifecycle
- Request is made to a server
- We get a response back with data in binary, text, HTML, or JSON
- We use that data in our application
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In the browser
- A user enters an address in the address bar (or clicks a link)
- A request is made to a server, which typically serves HTML
- Included in that HTML are links to images, fonts, stylesheets, and scripts
- Each one of those links means another request by the browser but without refreshing the page
- When all the external links have loaded, the page itself is finished loading
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Loaded JavaScript
- JavaScript can be written directly in HTML through a
scripttag - It can also be loaded externally through a
scripttag with asrcattribute - When the browser sees JavaScript, it attempts to run it immediately
- JavaScript can be written directly in HTML through a
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JavaScript implementations
- Each browser has its own JavaScript engine or implementation
- The Document Object Model is the interface between the loaded HTML and the JavaScript code we write
- Most browsers are converging on agreeing on web standards, but browsers need the ability to add proprietary features to CSS, JS, and the DOM (I'm looking at you Internet Explorer 😡)
- PLEASE ALSO BURN THIS INTO YOUR MEMORY. Always start with MDN when looking at JS documentation. W3 Schools is great for HTML and CSS, NOT SO MUCH FOR JAVASCRIPT.
(all hail Mozilla)
- INDENTATION AND PROPER STYLE ARE ALSO SUPER IMPORTANT MOVING FORWARD. Airbnb has an amazing JavaScript Style Guide if you're unsure about how to format your JS code. Trust me, learn to indent properly now before you end up in a curly bracket nightmare.
