24

I have always wondered when to use identifiers (for example, functions) with capital first letter instead of camel case. I always write my JS in camel case like this:

function doStuff() {}

var simpleVar = 'some stuff',
    myAry = [],
    myObj = {};

... But I know I am supposed to name some things with capital first letters. I just don't know WHEN this rule applies. Hope somebody can make things a bit clearer to me.

Dan Dascalescu
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patad
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3 Answers3

34

According to the book "Javascript: the good parts", you should only capitalise the first character of the name of a function when you need to construct the object by "new" keyword.

This is called "the Constructor Invocation Pattern", a way to inherits.

louis.luo
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19

The convention is to name constructor functions (i.e. functions that will be used with the new keyword) with starting capital.

function MyType(simpleVar) {
    this.simpleVar = simpleVar;
}

myObject = new MyType(42);
Peter-Paul van Gemerden
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    What about variables that happen to start with a capital letter, because they refer to an acronym - should the first letter, or the entire acronym be lowercased? Example: `ECBhandle` vs. `ecbHandle` (it does _not_ matter what ECB means). – Dan Dascalescu Dec 04 '13 at 12:39
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    @DanDascalescu: Personally, I treat acronyms the same as regular words, so in this case I would opt for `ecbHandle`. Other examples would be `parseXml` or `isbn`. This applies to constructor functions as well: e.g. `XmlParser`. – Peter-Paul van Gemerden Dec 05 '13 at 14:06
  • I like constants to be marked as ALLCAPS. Seems to work. – akauppi Mar 26 '15 at 14:11
6

The name convention states that class names are named with a first capital letter, I'm not sure how it's like with javascript, which is a prototype based language, but basically it's

class ClassName
var varName
function funcName()
Madara's Ghost
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