HTML / CSS / JavaScript Tutorial

JavaScript Tutorial

3. Statements

[this page | pdf | back links]

JavaScript statements identify instructions that are executed by the web browser. For example, the following statement tells the browser to write “Hello World” inside an HTML statement with the id attribute = "element":


               document.getElementById("element").innerHTML = "Hello World"


The same result can be achieved using several separate statements, e.g.:


               var d = document.getElementById("element");

var x = "Hello";

var y = " World";

var z = x + y;

d.innerHTML = z;


Statements are separated by semicolons and multiple statements are allowed on one line. JavaScript ignores multiple spaces (except in strings, i.e. within quotation marks). A common good practice is to put spaces around operators (e.g. =, + , …). Very long lines of code are also often frowned upon, and are usually broken after an operator.


Statements can (and often are) grouped together in code blocks, inside curly brackets, i.e. { … }. A particularly important example of the use of code blocks involves functions, which provide a means of executing on demand one or more statements, e.g.:


               function func() {

document.getElementById("element").innerHTML = "Hello";



Statements often start with a statement identifier. These are reserved words which cannot be used as variable names or for other purposes. A list of statement reserved words recognised by JavaScript is shown here. They include: break, continue, do, for, if, return, switch, throw, try, catch, var and while.


Most JavaScript programs contain many statements, which are executed one by one in the order in which they are written except when statement flow control is adjusted using statements such as for, if or while.


Contents | Prev | Next | JavaScript

Desktop view | Switch to Mobile