Introduction to JavaScript

What is a programming "Language"?

• Simply it is a formal (i.e. well-defined) language that is unambiguous as much as possible at all levels. Where in English words may have different meaning based on context, computers do not handle such ambiguity well and so formal languages try to eliminate such ambiguity as much as possible. The upside is that the rules for the languages' grammar or the syntax of the language are very clearly defined, making it easier to learn than a Human language.
• The purpose of the language is to instruct the computer, usually when given some input, to perform operations on the given input, producing some desired output.
• In that respect a program is like a recipe, ingredients (input) in, something to eat out.
• Computers only understand very simple things at the lowest levels, like:
  • Copy data from one place to another. (assignment)
  • Do numeric operations, such as addition and multiplication. (expressions)
  • Compare two values and determine if they are the same or not or if one is less or greater than the other. (conditionals, Boolean logic)
  • Jump around from one place to another in the program depending on the outcomes of the above comparisons. (loops and functions)
• Computer languages attempt to abstract the simple things computers do to a higher level to make things easier for the programmer. Some languages do so better than others.
• Some languages may be described as higher or lower level. This is usually meant to describe how close the syntax is the "lowest" level language assembly or machine language (ML) which is the native language of any computer and consists of very simple instructions that individually usually do nothing more than one of the four above things. Programming in assembly is usually regarded as tedious and often difficult, making for more mistakes that cause program crashes, especially for large programs. And so higher level languages were developed that made making mistakes less likely allowed the incorporation of libraries and more expressive code to abstract away common tasks that might take a lot of effort to develop in a lower level language.

What is the "syntax" of a computer language?

It is the grammar, or rules for the language, just as English does, computer languages have similar rules, but much more limited range of expression.

Often times programmers may describe the syntax of a programming language in terms of Lego bricks. Things like statements in such languages are like bricks that can then be snapped into a language anywhere a statement would go, and in this way assembling a program can be like snapping Lego bricks together. You have many different kinds of statements, but any kind of statement can be snapped into a statement spot. When learning a computer language it may be useful to employ this kind of mindset.

For this class we will learn JavaScript aka ECMAScript. It is incorporated into almost every browser, and also stand-alone as interpreters/compilers such as node.js or "node" and SpiderMonkey or "js". One of the reasons for the choice of this language over others is that it should not disadvantage anyone moving on to CS201/CS202 which use C/C++ which are structurally similar, it is widely used in industry and so there are a large number of free online informational resources and coupled with a simple text editor and web browser, everyone already has a development environment installed on their computer, making the cost of entry into JavaScript development very low indeed.