JavaScript is a scripting or programming language that allows you to implement complex features on web pages — every time a web page does more than just sit there and display static information for you to look at — displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. — you can bet that JavaScript is probably involved. It is the third layer of the layer cake of standard web technologies.

Example of what JavaScript can do:

                    alert("Hello World!")
                

There are many ways we can output information in Javascript:

                    Writing into an HTML element, using innerHTML
                    Writing into the HTML output using code document.write().
                    Writing into an alert box, using window.alert().
                    Writing into the browser console, using console.log().
                

Try it yourself, type: alert("enter message here");

• A computer program is a list of "instructions" to be "executed" by a computer.
• In a programming language, these programming instructions are called statements.
• A JavaScript program is a list of programming statements.

Example of a statement:

                    document.getElementById("demo").innerHTML = "Hello Dolly.";
                

JavaScript Variables

In a programming language, variables are used to store data values.

JavaScript uses the var keyword to declare variables.

An equal sign is used to assign values to variables.

In this example, x is defined as a variable. Then, x is assigned (given) the value 6:

                    var x;
                    x = 6;
                

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Arithmetic Operators:

• +
• -
• *
• /

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