- JavaScript and Java are completely different languages, both in concept and design.
- JavaScript was invented by Brendan Eich in 1995, and became an ECMA standard in 1997.
- ECMA-262 is the official name of the standard. ECMAScript is the official name of the language.
JavaScript is one of the 3 languages all web developers must learn:
- HTML to define the content of web pages
- CSS to specify the layout of web pages
- JavaScript to program the behavior of web pages
NB:it is also call astrinity.
- The Original JavaScript ES1 ES2 ES3 (1997-1999)
- The First Main Revision ES5 (2009)
- The Second Revision ES6 (2015)
- All Yearly Additions (2016, 2017, 2018, 2019, 2020)
- The
<script></script>tagIn HTML, JavaScript code is inserted between <script> and </script> tags.
- example
<script>
document.getElementById("demo").innerHTML = "My First JavaScript";
</script>- The
<head></head>tagIn this example, a JavaScript function is placed in the section of an HTML page.
The function is invoked (called) when a button is clicked:
<!DOCTYPE html>
<html>
<head>
<script>
function myFunction() {
document.getElementById("demo").innerHTML = "Paragraph changed.";
}
</script>
</head>
<body>
<h2>Demo JavaScript in Head</h2>
<p id="demo">A Paragraph</p>
<button type="button" onclick="myFunction()">Try it</button>
</body>
</html>- The
<body></body>tagIn this example, a JavaScript
functionis placed in the<body></body>section of an HTML page.
The function is invoked (called) when a button is clicked:
NB:Placing scripts at the bottom of the element improves the display speed, because script interpretation slows down the display.
JavaScript can "display" data in different ways:
- Writing into an HTML element, using innerHTML.
- Writing into the HTML output using document.write().
- Writing into an alert box, using window.alert().
- Writing into the browser console, using console.log().
- javaScript accepts both
double and singlequotes - attributes : a collection of objects that belong to a built-in Attr class, with name and value properties.
- javascript can change HTML style (css)
document.getElementById("demo").style.fontSize = "35px";- javascript can hide HTML elements
document.getElementById("demo").style.display = "none";