Now for a bit about JavaScript and C-style code. First and foremost, if you are unfamiliar or think you are familiar, but really aren’t, (because of say, the welcoming C-style syntax) with JavaScript consider reading JavaScript: The Good Parts. It is a quick, light read that provides invaluable insight into the language. JS is an immensely expressive language but some of the baggage surrounding it can make it seem like little more than a toy language that is intolerable to code in and should generally be avoided at all costs. This simply isn’t true, so go on, have a read.
Update: Indentation and brace style should follow the 1TBS/OTBS style.
When programming in JS always keep in mind that JS doesn’t come with a linker, so everything is put in the global namespace unless you explicitly state not to. All program variables should be kept either within a lambda scope e.g.
var a = ‘foo’,
b = function () {…},
c = ‘bar’, …
)());
or within a namespace e.g.
MYPROGRAM.a = ‘foo’;
MYPROGRAM.b = function b (…) {…};
MYPROGRAM.c = ‘bar’;
-or-
a: ‘foo’,
b: function b (…) {…},
c: ‘bar’
};
Also, all variables should be declared with the var keyword, otherwise the JS interpreter will automatically link it to the global object. Further, unlike many other C-style languages JS does not have block scope (neither does PHP for that matter). In languages with block scope it is suggested to not declare variables until they are used. Since both PHP and JS only have functional scope, variables should be declared at the top of the function in which they are used rather than right before they are used.
Since JS provides no linkeranything can overwrite anything else, and no runtime warning or errors are provided when such an event occurs. A lot of code in JS seems to be copied and pasted from elsewhere and this code could very well have strange interactions with your programs if the original author forgot to properly declare a variable or named one of his functions the same as yours. Always encapsulate your program variables and keep them out of the global namespace. When using a namespace, keep the namespace as all caps, this is to differentiate it from other methods or functions.
Generally, when naming function or methods, the name should start with a lower case letter, unless it is a constructor function. If it is a constructor function it should start with an upper case letter. e.g.
this.hello = function () {
alert(bar);
}
}
var myFoo = new Foo("bar");
myFoo.hello(); //"bar"
Since we are primarily dealing with web languages it is best not to mix up code style between different C-style languages such as JS and PHP, as during the course of a day you will most likely be working in many languages. In either language either of the following are acceptable:
bar;
}
if (foo)
{
bar;
}
if (foo)
bar;
However, the first is the preferred way of writing it. This is due to a limitation in JS. JS implicitly inserts end of statement characters on new lines. So something like:
{
foo: ‘bar’
};
may look like it is returning a new object with the property foo with the value ‘bar.’ However, it is actually returning undefined and the object literal statement is never reached. What is really meant is:
foo: ‘bar’
};
Moreover, it is very easy to make a mistake such as:
bar();
baz();
which was meant to mean:
bar();
baz();
}
but really means:
bar();
}
baz();
It is preferred that when declaring arrays or objects that their literal forms are used. So instead of:
b = new Array();
write:
b = [];
The use of whitespace is paramount when writing code. It increases legibility significantly. The suggested use of whitespace is as follows:
- Use a space before and after any operator e.g. /, +, *, -, &&, etc.
- Use a space after a function declaration and the beginning and end of the argument definition e.g. function foo (a, b, c) { }. This helps differentiate between a function definition and a function invocation.
- Use a space after semi-colons
When testing for values in JS always use === or !== operators. Their == and != counterparts do not do what you might think they do and should generally be avoided.
If a function requires many arguments consider putting the arguments in an options object and passing the object into the function instead of having a long list of arguments which may or may not be optional. This alleviates the need to have to remember the order of all the arguments and allows for more verbose code, too. For example:
foo(1, 2, 3);
can be rewritten as
foo({
bar: 1,
qoz: 2,
baz: 3
});
More to come later…