JavaScript syntax is the rules, how JavaScript programs are constructed.
A computer program is a list of "instructions" to be "executed" by the computer.
In a programming language, these program instructions are called statements.
JavaScript is a programming language.
JavaScript statements are separated by semicolon.
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In HTML, JavaScript programs can be executed by the web browser. |
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JavaScript statements are composed of:
Values, Operators, Expressions, Keywords, and Comments.
The JavaScript syntax defines two types of values: Fixed values and variable values.
Fixed values are called literals. Variable values are called variables.
The most important rules for writing fixed values are:
Numbers are written with or without decimals:
Strings are text, written within double or single quotes:
Expressions can also represent fixed values:
In a programming language, variables are used to store data values.
JavaScript uses the var keyword to define 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:
JavaScript uses an assignment operator ( = ) to assign values to variables:
JavaScript uses arithmetic operators ( + - * / ) to compute values:
JavaScript keywords are used to identify actions to be performed.
The var keyword tells the browser to create a new variable:
Not all JavaScript statements are "executed".
Code after double slashes // or between /* and */ is treated as a comment.
Comments are ignored, and will not be executed:
All JavaScript identifiers are case sensitive.
The variables lastName and lastname, are two different variables.
JavaScript does not interpret VAR or Var as the keyword var.
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It is common, in JavaScript, to use camelCase names. You will often see names written like lastName (instead of lastname). |
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JavaScript uses the Unicode character set.
Unicode covers (almost) all the characters, punctuations, and symbols in the world.
For a closer look, please study our Complete Unicode Reference.
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