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What are JavaScript basics?
JavaScript basics include an overview of JavaScript. JavaScript is a dynamic computer programming language. It is lightweight and most commonly used as a part of web pages, whose implementations allow a client-side script to interact with the user and make dynamic pages. It is an interpreted programming language with object-oriented capabilities.
Variables
Like many other programming languages, JavaScript has variables. Variables can be thought of as named containers. You can place data into these containers and then refer to the data simply by naming the container.
Scope of Variables
The scope of a variable is the region of your program in which it is defined. JavaScript variables have only two scopes.
- Global Variables − A global variable has a global scope which means it can be defined anywhere in your JavaScript code.
- Local Variables − A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.
JavaScript can be implemented using JavaScript statements that are placed within the <script>... </script>.
You can place the <script> tags, containing your JavaScript, anywhere within your web page, but it is normally recommended that you should keep it within the <head> tags.
Let us take a simple example to print out "Hello World". We added an optional HTML comment that surrounds our JavaScript code. This is to save our code from a browser that does not support JavaScript.
The comment ends with a "//-->". Here "//" signifies a comment in JavaScript, so we add that to prevent a browser from reading the end of the HTML comment as a piece of JavaScript code. Next, we call a function document.write, which writes a string into our HTML document.
This function can be used to write text, HTML, or both. Take a look at the following code.
<html>
<body>
<script>
<!--
document.write("Hello World!")
//-->
</script>
</body>
</html>
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