<!DOCTYPE html>
<html>
<head>
<script>
function myFunction(){
document.getElementById("demo").innerHTML="paragraph changed.";
}
</script>
</head>
<body>
<h1> Java Script In Head</h1>
<p id="demo"> A paragraph.</p>
<button type = "button" onclick="myFunction()">Try it</button>
</body>
</html>
============================
we can write js at head element or body element
but preferred one is body element
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Head</h1>
<p id="demo"> A paragraph.</p>
<button type = "button" onclick="myFunction()">Try it</button>
<script>
function myFunction(){
document.getElementById("demo").innerHTML="paragraph changed.";
}
</script>
</body>
</html>
===================
javascript output
* java script does not have any built-in print or display functions.
javascript can "display" data in different ways:
1. writing into an alert box, using window.alert().
2. writing into the HTML output using document.write().
3. writing into an HTML element, using innerHTML.
4. writing into the browser console, using console.log().
1. window.alert
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> A paragraph with alert msg.</p>
<script>
window.alert(5+8);
}
</script>
</body>
</html>
2. document.write
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> A paragraph with alert msg.</p>
<script>
document.write(5+8);
</script>
</body>
</html>
or
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> document.write() after an HTML document fully loaded
<b> delete all existing HTML.</p>
<button onclick="document.write(10+11)"> Click </button>
</body>
</html>
3. innerHTML
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> document.write() after an HTML document fully loaded
<b> delete all existing HTML.</p>
<p id="demo"></P>
<script>
document.getElementById("demo").innerHTML=5+6;
</script>
</body>
</html>
======================
lesson 3
--------
JavaScript syntax : JavaScript syntax is the set of rules, How JavaScript programs are constructed.
JavaScript Programs :
A computer program is a list of "instructions" to be "executed" by the computer.
In a programming language, these program instructions are called statements.
JavaScript is a programming language.
JavaScript statements are separated by semicolons.
Ex:
<!DOCTYPE html>
<html>
<body>
<h1> Java Script statements</h1>
<p> The variables x,y and z are assigned the values 10,20 and 30;</p>
<p id="demo"></P>
<script>
var x=10;
var y=20;
var z=x+y;
document.getElementById("demo").innerHTML=z;
</script>
</body>
</html>
JavaScript Statements
<html>
<head>
<script>
function myFunction(){
document.getElementById("demo").innerHTML="paragraph changed.";
}
</script>
</head>
<body>
<h1> Java Script In Head</h1>
<p id="demo"> A paragraph.</p>
<button type = "button" onclick="myFunction()">Try it</button>
</body>
</html>
============================
we can write js at head element or body element
but preferred one is body element
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Head</h1>
<p id="demo"> A paragraph.</p>
<button type = "button" onclick="myFunction()">Try it</button>
<script>
function myFunction(){
document.getElementById("demo").innerHTML="paragraph changed.";
}
</script>
</body>
</html>
===================
javascript output
* java script does not have any built-in print or display functions.
javascript can "display" data in different ways:
1. writing into an alert box, using window.alert().
2. writing into the HTML output using document.write().
3. writing into an HTML element, using innerHTML.
4. writing into the browser console, using console.log().
1. window.alert
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> A paragraph with alert msg.</p>
<script>
window.alert(5+8);
}
</script>
</body>
</html>
2. document.write
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> A paragraph with alert msg.</p>
<script>
document.write(5+8);
</script>
</body>
</html>
or
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> document.write() after an HTML document fully loaded
<b> delete all existing HTML.</p>
<button onclick="document.write(10+11)"> Click </button>
</body>
</html>
3. innerHTML
<!DOCTYPE html>
<html>
<body>
<h1> Java Script In Body Alert message</h1>
<p> document.write() after an HTML document fully loaded
<b> delete all existing HTML.</p>
<p id="demo"></P>
<script>
document.getElementById("demo").innerHTML=5+6;
</script>
</body>
</html>
======================
lesson 3
--------
JavaScript syntax : JavaScript syntax is the set of rules, How JavaScript programs are constructed.
JavaScript Programs :
A computer program is a list of "instructions" to be "executed" by the computer.
In a programming language, these program instructions are called statements.
JavaScript is a programming language.
JavaScript statements are separated by semicolons.
Ex:
<!DOCTYPE html>
<html>
<body>
<h1> Java Script statements</h1>
<p> The variables x,y and z are assigned the values 10,20 and 30;</p>
<p id="demo"></P>
<script>
var x=10;
var y=20;
var z=x+y;
document.getElementById("demo").innerHTML=z;
</script>
</body>
</html>
JavaScript Statements
