Usage
Description¶
How to Use JavaScript
Usage¶
Embedded¶
Embedded in head or body elememt
<script>
// Logic
</script>
External¶
External File Link in head or body element
<script src="path/to/global.js"></script>
<script src="path/to/section.js"></script>
Statements¶
- end in semicolon
- whitespaces ignored
- can put multiple statments on a single line
- statements can span lines
Execution Context¶
Memory Allocation Phase-
Functs and vars get stored into mem as key-val pairs
Code Execution Phase-
Thread of execution, whereby vals of functs and vars are updated in order
When a function is called, a new Execution Context is created inside the calling execution context.
Parsing Order¶
- HTML file is parsed until it hits
<script>tag - Parsing is paused until script is fetched and executed.
- JS files are executed in order of appearance in the doc.
async Attrib¶
<script src="script.js" async>
- js file is downloaded at same time as HTML parsing.
- When file is finished downloading, HTML parsing is paused until code is executed.
defer Attrib¶
<script src="script.js" defer>
- file is download during HTML parsing
- file executes post parsing
- deferred scripts execute in order of appearance