JavaScript

[01] JavaScript Intro

MorningPhys 2015. 7. 13. 16:54

Examples in Each Chapter

 

<!DOCTYPE html>
<html>
<body>

<h1>My First JavaScript</h1>

<button type="button" onclick="document.getElementById('demo').innerHTML = Date()">
     Click me to display Date and Time.

</button>

<p id="demo"></p>

</body>
</html>  

 

JavaScript Introduction

JavaScript is the most popular programming language in the world.

This page contains some examples of what JavaScript can do.

 

JavaScript Can Change HTML Content

One of many HTML methods is getElementById().

This example uses the method to "find" an HTML element (with id="demo"), and changes the element content (innerHTML) to "Hello JavaScript": 

 <!DOCTYPE html>
<html>
<body>

<h1>What Can JavaScript Do?</h1>

<p id="demo">JavaScript can change HTML content.</p>

<button type="button" onclick="document.getElementById('demo').innerHTML = 'Hello JavaScript!'">
Click Me!</button>

</body>
</html>

 

JavaScript Can Change HTML Attributes

This example changes an HTML image, by changing the src attribute of an <img> tag:

 

<img id="myImage" onclick="changeImage()" src="pic_bulboff.gif" width="100" height="180">

<p>Click the light bulb to turn on/off the light.</p>

<script>
function changeImage() {
    var image = document.getElementById('myImage');
    if (image.src.match("bulbon")) {
        image.src = "pic_bulboff.gif";
    } else {
        image.src = "pic_bulbon.gif";
    }
}
</script> 

 

JavaScript Can Change HTML Styles (CSS)

Changing the style of an HTML element, is a variant of changing an HTML attribute:

 document.getElementById("demo").style.fontSize = "25px";

 

<script>
function myFunction() {
    var x = document.getElementById("demo");
    x.style.fontSize = "25px";          
    x.style.color = "red";
}
</script>

<button type="button" onclick="myFunction()">Click Me!</button> 

 

JavaScript Can Validate Data

JavaScript is often used to validate input:

 

<h1>JavaScript Can Validate Input</h1>

<p>Please input a number between 1 and 10:</p>

<input id="numb" type="number">

<button type="button" onclick="myFunction()">Submit</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x, text;

    // Get the value of the input field with id="numb"
    x = document.getElementById("numb").value;

    // If x is Not a Number or less than one or greater than 10
    if (isNaN(x) || x < 1 || x > 10) {
        text = "Input not valid";
    } else {
        text = "Input OK";
    }
    document.getElementById("demo").innerHTML = text;
}
</script> 

 

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