Difference between revisions of "JavaScript"
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====Change HTML Attribute Values==== | ====Change HTML Attribute Values==== | ||
| − | + | In this example JavaScript changes the value of the src (source) attribute of an <img> tag: | |
| + | <syntaxhighlight lang="javascript"> | ||
<button onclick="document.getElementById('myImage').src='pic_bulbon.gif'">Turn on the light</button> | <button onclick="document.getElementById('myImage').src='pic_bulbon.gif'">Turn on the light</button> | ||
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<button onclick="document.getElementById('myImage').src='pic_bulboff.gif'">Turn off the light</button> | <button onclick="document.getElementById('myImage').src='pic_bulboff.gif'">Turn off the light</button> | ||
| − | + | </syntaxhighlight> | |
<br /> | <br /> | ||
====Change HTML Styles - CSS==== | ====Change HTML Styles - CSS==== | ||
| − | + | Changing the style of an HTML element, is a variant of changing an HTML attribute: | |
<syntaxhighlight lang="javascript"> | <syntaxhighlight lang="javascript"> | ||
| − | + | document.getElementById("demo").style.fontSize = "35px"; | |
</syntaxhighlight> | </syntaxhighlight> | ||
| Line 84: | Line 85: | ||
<br /> | <br /> | ||
====Hide HTML Elements==== | ====Hide HTML Elements==== | ||
| − | + | Hiding HTML elements can be done by changing the display style: | |
<syntaxhighlight lang="javascript"> | <syntaxhighlight lang="javascript"> | ||
| − | + | document.getElementById("demo").style.display = "none"; | |
</syntaxhighlight> | </syntaxhighlight> | ||
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<br /> | <br /> | ||
====Show HTML Elements==== | ====Show HTML Elements==== | ||
| − | + | Showing hidden HTML elements can also be done by changing the display style: | |
<syntaxhighlight lang="javascript"> | <syntaxhighlight lang="javascript"> | ||
| − | + | document.getElementById("demo").style.display = "block"; | |
</syntaxhighlight> | </syntaxhighlight> | ||
<br /> | <br /> | ||
Revision as of 13:53, 14 October 2019
https://www.w3schools.com/js/default.asp
JavaScript and Java are completely different languages, both in concept and design.
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
Web pages are not the only place where JavaScript is used. Many desktop and server programs use JavaScript. Node.js is the best known. Some databases, like MongoDB and CouchDB, also use JavaScript as their programming language.
Contents
What JavaScript can do
What JavaScript can do / What is used for / some of the most important methods:
- JavaScript Can Change HTML Content
- JavaScript Can Change HTML Attribute Values
- JavaScript Can Change HTML Styles (CSS)
- JavaScript Can Hide HTML Elements
- JavaScript Can Show HTML Elements
Installation
IDE for JavaScript
Control flow statements
If statements
For Loops
While Loops
Methods
Some of the most important methods
https://www.w3schools.com/js/js_intro.asp
Change HTML Content
This example uses the method to "find" an HTML element (with id="demo") and changes the element content (innerHTML) to "Hello JavaScript":
document.getElementById("demo").innerHTML = "Hello JavaScript";
Change HTML Attribute Values
In this example JavaScript changes the value of the src (source) attribute of an tag:
<button onclick="document.getElementById('myImage').src='pic_bulbon.gif'">Turn on the light</button>
<img id="myImage" src="pic_bulboff.gif" style="width:100px">
<button onclick="document.getElementById('myImage').src='pic_bulboff.gif'">Turn off the light</button>
Change HTML Styles - CSS
Changing the style of an HTML element, is a variant of changing an HTML attribute:
document.getElementById("demo").style.fontSize = "35px";
Hide HTML Elements
Hiding HTML elements can be done by changing the display style:
document.getElementById("demo").style.display = "none";
Show HTML Elements
Showing hidden HTML elements can also be done by changing the display style:
document.getElementById("demo").style.display = "block";
