Introductory JavaScript Made Easy Training Tutorial

JavaScript is considered a dynamic programming language. It was first released with Netscape Navigator in 1995. Originally called LiveScript, the name was changed when Netscape Navigator added support for the machine language Java. Learn this and more during this lecture.

Although the two programming languages Java and JavaScript have similar names, they are completely different in function. Java was created by Sun Microsystems and is used as a general programming language. JavaScript was created by the people who made the Web browser Netscape Navigator and is used to animate and add user interactions to webpages. Learn this and more during this lecture.

The <script>...</script> tag is used to insert JavaScript code into your HTML document. It tells the web browser where your JavaScript starts and the lines of code in between the tags contain all your coding. Learn this and more during this lecture.

The most effective use of JavaScript is to create an external .jsfile. Using an external JavaScript file allows your browser to preload, or cache, all the JavaScript code for your whole website. This minimizes your users wait time as pages on your website will load faster, making for a better user experience. Learn this and more during this lecture.

The uses for JavaScript are almost endless. They range from validating the information users input in a form to embedded games on your webpage. The most widely recognized use of JavaScript is probably the Google Search Engine homepage. JavaScript has allowed them to remove extraneous items from the page to leave a clean, minimalist look. Learn this and more during this lecture.

JavaScript statements are the commands to the browser to execute the code you input.Much like CSS, the semicolon (;) is used to separate JavaScript statements and allows for many statements to be typed on a single line. Usually there is also a semicolon at the end of executable statements. Learn this and more during this lecture.

JavaScript code is simply a sequence of JavaScript statements. Each statement is executed by the browser in the order they are entered into your HTML document or external .js file. Learn this and more during this lecture.

In JavaScript, extraneous whitespace is ignored. Learn this and more during this lecture.

JavaScript is case sensitive. Cases in corresponding functions and variables must match exactly or they will not be rendered properly. Most JavaScript code is written in camelCase, which means compound words written with the first letter in lowercase and subsequent words with their first letter capitalized. Learn this and more during this lecture.

JavaScript allows you to break up a line of code within a text string with a backslash (\). Learn this and more during this lecture.

Comments in JavaScript are primarily used to explain what the code is for or to make it more readable. Single line comments start with a double forward slash (//), but do not have an end tag. Learn this and more during this lecture.

Multi-line comments in JavaScript start with a forward slash and an asterisk (/*) and end with an asterisk and a forward slash (*/). This allows for breaking your comments up into many lines, making it more readable for later editing. Learn this and more during this lecture.

You can also add comments to the end of a line of JavaScript code. These are considered single line comments and begin with a double forward slash (//). Learn this and more during this lecture.

You can use the single line comment "tag" (//), or the multi-line comment “tags” (/*…*/) to stop the execution of a line, or multiple lines, of code. This works because JavaScript ignores any text entered after the comment “tags”. Learn this and more during this lecture.

Much like algebra, JavaScript uses letters as containers for storing information, for example: var x=7;. In the previous example, the letter "x" is assigned a numerical value of 7, declaring that any variables with the letter "x" will have a value of 7. Learn this and more during this lecture.

JavaScript variables can have either a numerical or textual value. The syntax for each variable is different. When assigning a numerical value to a variable you only need to input the number: var a=7;. Learn this and more during this lecture.

When creating variables using JavaScript, you “declare” the variable by giving it a value. JavaScript variables are declared using the keyword var. For ease of reading within your code, you can declare a variable and on the next line assign a value to that variable. You can also assign a value on the same line as you declare a variable. Learn this and more during this lecture.

If you re-declare a JavaScript variable, that has previously been given a value, it does not lose its value. Learn this and more during this lecture.

In JavaScript a variable that is not given a specific value is considered undefined. The value of a variable is something that has to be calculated or something that may be provided later, like user inputted data. Learn this and more during this lecture.

When programming code with JavaScript, you can have many variables in one statement. This is achieved by starting the statement with var and listing your variables all separated bycommas. Learn this and more during this lecture.

In JavaScript a "local" variable is a variable that is contained within a function. It will not be recognized by any other function in your full JavaScript coding. Because of this, you can have local variables in other functions that have the same value. When a function is complete any local variables are deleted. Learn this and more during this lecture.

Variables in JavaScript can have different data types. This allows variables to be considered "dynamic". Learn this and more during this lecture.

You can attribute a null value to variables to empty them. A null value data type is different from an undefined data type, because a null value data type has been labeled as "null" and not just left empty. Learn this and more during this lecture.

In JavaScript there is only one type of number. Numbers can be written with or without decimals and extra large or extra small numbers can be expressed using scientific or exponential notations. Learn this and more during this lecture.

A JavaScript String object is simply any variable ascribed a value in text form. Learn this and more during this lecture.

Boolean data types have only two values TRUE and FALSE. Any variable labeled with either TRUE or FALSE is considered a Boolean data type. Learn this and more during this lecture.

In JavaScript, arrays are actually objects, not a separate “data type”. An array is simply a single variable with many different values. You access the values by referencing index numbers allocated to each value. Defining variables in an array makes it easier to find a specific value in a long list of values. Learn this and more during this lecture.

In JavaScript an object is delineated by curly brackets ({ }). Inside the curly brackets are the object’s properties. Learn this and more during this lecture.

In JavaScript everything is an object. Strings, Dates, Arrays and Functions are just a few examples. You can also create your own objects using JavaScript. The only items in JavaScript that are not considered objects are data types that are either null or undefined. Learn this and more during this lecture.

Object properties determine the state of an object in JavaScript and are the values associated with the object. Learn this and more during this lecture.

Methods are actions that can be performed on objects. Similar to functions they are specific to the object they are associated with. Learn this and more during this lecture.

A function is a “subprogram” in JavaScript that is used to manipulate values or objects to achieve a specific result.Functions are code blocks that are executed when someone “calls” or initiates the function. Functions are first class objects and are considered FUNCTION objects in JavaScript. Learn this and more during this lecture.

Functions can also be used to return a value to where the “call” or initiation of the code, was made from. To do this you use the return statement. When using the return statement, the specific function will stop executing and return the value you specify. It is important to remember that the JavaScript code as a whole does not stop executing when a return statement is used, only the specific function containing the return statement. Learn this and more during this lecture.

When you call, or initiate, a function you pass values to it. These are called parameters and the values used for parameters are called arguments. When assigning arguments to parameters the values listed for the arguments must be in the same order as your listed parameters. Learn this and more during this lecture.

In JavaScript, when you assign values to any variables that have not previously been declared, those variables are considered to be global variables. It does not matter, in this instance, if the undeclared variable is contained within a function, it will still be considered a global variable. Learn this and more during this lecture.

Operators, in JavaScript are signs or symbols used to assign or calculate values, such as the plus sign (+). Arithmetic operators are used in the calculation of numerical values, just as in regular arithmetic. The values used with operators are called operands. Learn this and more during this lecture.

Assignment operators are used to assign different values to variables. Learn this and more during this lecture.

The + operator can be used to add strings, or text values, together and is called concatenation (combining into one). It can also be used to add strings and numbers together. Learn this and more during this lecture.

Comparison operators are generally used to test for true or false. They are used in logical statements to test for a difference or equality in variables or values, to return an answer of true or false. They can also be used in conditional statements to compare a set of values and take an action based on the result of the comparison. Learn this and more during this lecture.

Logical operators are used to determine the logic between values and variables. Logical operators are generally used with Boolean values and will return a Boolean result (true or false). However they can be used with non-Boolean values and can return a non-Boolean result. Learn this and more during this lecture.

The conditional, or ternary, operator is the question mark (?). It can be used as a shortcut to an if…else statement in JavaScript. It is used to evaluate a true/false statement and returns a value to a variable depending on the outcome. Learn this and more during this lecture.

In JavaScript, conditional statements are used when you want to perform different actions for different choices. Learn this and more during this lecture.

The switch statement is used to select specific code to execute out of several code blocks. It is similar to an if…else statement, but is easier to use to allow the code to follow a specific path out of many. Learn this and more during this lecture.