Introduction to Javascript

## Javascript: The big picture
            <a href="https://developer.mozilla.org/en-US/docs/Glossary/JavaScript" target="_blank">A Quick History</a>
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            ## HTML 
            #### Content
            The markup language that we use to structure and give meaning to our web content, for example:
            - defining page elements (nav, headings, etc)
            - embedding media (images, videos, audio, etc).
            - managing connected files (`.css`, `.js`, `.png`, etc)
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            ## CSS 
            #### Presentation
            A language of style rules that we use to apply styling to our HTML content, such as 
            - colour
            - typography
            - layout
            - animation (when used for presentation)
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            ## Javascript 
            #### Behaviour
            The official programming language of the browser. It does the things HTML and CSS can't, such as:
            - dynamically update content
            - control media such as video
            - animation of images, svgs, etc
            - math, if you're into that kind of thing
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            ## Syntax Considerations
            - JavaScript is case-sensitive
                - `myvar` is not the same as `myVar`
            - hyphens (-) are not allowed in variable names
                - CSS: `border-top`
                - JS: `borderTop`
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            ## Coding Conventions
            - indent blocks with 2 spaces
            - use camelCase for variable names;
            - add spaces around operators (`=`, `+`, `*`)
            - add spaces after commas (unless at end of line)
            - limit line length to 80 characters (for readability)
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            ## Javascript Value Types
            There are more but we don't need to know about them.
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            ## Primitive Types
            - **Strings**: used to represent textual data.
            - **Numbers**: floating point (integers are a lie).
            - **Booleans**: `true` and `false`.
            - **Null**: has exactly one value - null.
            - **Undefined**: a variable that has not been assigned a value has the value undefined.
                - never manually assign a variable as `undefined`.
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            ## Complex Types
            - **Arrays**: a list of values, including other arrays.
            - **Objects**: a collection of name/value pairs (properties).
            - **Functions**: a block of reusable code that accepts arguments (input data) and may or may not return a value.