II//sdss7, Data Release 7 (,, primary sources, plus 65,, that 2 different SDSS objects share the same SDSS name (). 1. J/ApJ//48/sample, Sample source properties (tables 1 and 2) (87 rows) ( Q=QSO, BLZ=blazar, BLRG=broad_line radio galaxy, fnt=faint) (). [0/1] Fmag quality of the PSF fitting Qfit () (CODE_QUALITY). f_Fmag, [0/7] Quality flag (best=1) on Fmag (Note 2) ().

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JavaScript has many great style guides. Thus, there is no need to write yet another one. Instead, this chapter describes meta style rules and surveys existing style guides and established best practices. It also mentions practices I like that are more controversial. The idea is to complement existing style guides rather than to replace them. These are style guides that I like: There are two important rules for writing consistent code.

The first rule is that, ,etacode you start a new project, you should come up with a style, document it, and follow it everywhere. The larger the team, the more important it is to check for adherence to the style automatically, via tools such as JSHint. When it comes to style, there are many decisions to make.

Most of them have generally agreed-upon answers. Others have to be defined per project. Everyone knows that debugging is twice as hard as writing a program in the first place. So if you are as clever as you can be when you write it, how will you ever debug it?

For most code, the time used for reading it is much greater than the time used for writing it. It is thus important to make the former as easy as possible. Here are some guidelines for doing that:. Most code bases are filled with new ideas and concepts.

That means that if you want to work with a code base, you need to learn those ideas and concepts. In contrast to textbooks, the added challenge with code is that people will not read it linearly. They jetacode jump in anywhere and should be able to roughly understand what is going on. Three parts of a code base help:.

Much cleverness is directed at these optimizations. On one hand, JavaScript engines are becoming increasingly smart and automatically optimize the speed of code that follows established patterns. metacide

6.2 Metacode

Sometimes you have no choice but to optimize the performance of your code. If you do, be sure to measure and optimize metaocde right pieces. A majority of JavaScript programmers agree on the following best practices: I recommend never deviating from this rule. I even prefer the first of the following two conditions, even though they are equivalent: In languages where braces delimit blocks of code, a brace style determines where you put those braces.


Two brace styles are most common in C-like languages such as Java and JavaScript: Allman style and 1TBS. If a statement contains a block, that block is considered as somewhat separate from the head of the statement: Here, a block is more closely associated with the header of its statement; it starts after it, in the same line.

The bodies of control flow statements are always put in braces, even if there is only a single statement. It has metacoce inherited from Java and most style guides recommend it.

Mehacode reason for that is objective. If you return an object literal, you must put the opening brace in the same line as the keyword returnlike this otherwise, automatic semicolon insertion inserts a semicolon after returnmeaning that nothing is returned; see Pitfall: ASI can unexpectedly break up statements:.

Obviously, an object literal is not a code block, but things look more consistent and you are less likely to make mistakes if both are formatted the same way. As an exception, I omit braces if a statement can be written in a single line. Several constructors produce objects that can also be created by literals. The latter is normally the better choice: Initializing an array with elements avoid! This section collects examples of unrecommended cleverness.

In the latter case, they return a value and while there is a mnemonic, you still need to think to figure out what is going on: Changing undefined explains why.

The shift operator can be used to convert a number to an integer. However, it is usually better to use a more explicit alternative such as Math. Netacode to Integer gives an overview of all ways of converting to integer. Sometimes you can be clever in JavaScript—if the cleverness has become an established pattern.

Using the Or operator to provide default values is a common pattern—for example, for parameters: For details and more examples, consult Pattern: If you use methods generically, you can abbreviate Object. The following two expressions are equivalent: It is a hack you are accessing a prototype property via an instance. But it reduces clutter, and I expect engines to eventually optimize this pattern.

I like relatively tight whitespace. The model is written English: And there are spaces after commas: The rationale is that this is what a named function expression looks like if you remove the name:. This helps with reading, because it is easier to make out the scope of the operator: The advantages of this approach are that deleting, inserting, and rearranging lines is simpler and the lines are automatically indented correctly.

As an addendum to the previous rule: The preceding code has the same effect and intention as the following code, which is why it should be written that way:.


For constructors, it is important to use strict mode, because it protects you against forgetting the new operator for instantiation. And you should be aware that you can return any object in a constructor. More tips for using constructors are mentioned in Tips for Implementing Constructors. Coerce a value to a type via BooleanNumberStringObject used as functions—never use those functions as constructors. The rationale is that this convention is more descriptive: The rationale is that such functions are easier to call and understand.

I also like to keep object-oriented and functional mechanisms separate: This is more self-explanatory and safer than comparing with undefined or checking for truthiness:. Whenever you are considering a style question, ask yourself: A Meta Code Style Guide. Popular Conventions on GitHub analyzes GitHub code to find out which coding conventions are most frequently used.

JavaScript, the winning style examines what the majority of several popular style guides recommend.

RAVE – the Radial Velocity Experiment

Code Should Be Consistent. How much whitespace after parentheses, between statements, etc. Code Should Be Easy to Understand. First, familiar things are easier to understand. That can mean that using familiar, slightly more verbose, constructs can be preferable. Second, humans read tokens, not characters. Therefore, redBalloon is easier to read than rdBlln. Good code is like a textbook Most code bases mwtacode filled with new ideas and concepts. Three parts of a code base help: Code should explain what is happening; it should be self-explanatory.

To write such code, use descriptive identifiers and break up long functions or methods into smaller subfunctions. If those functions are small enough and have meaningful names, you can often avoid comments. Comments should explain why things are happening. If you need to know a concept to understand the code, you can either include the name of the concept in an identifier or mention it metafode a comment.

Someone reading the code can then turn to the documentation to find out more about the concept. Documentation should fill in the blanks left by the code and the comments. It should tell you how to get started with the code base and provide you with the big picture. It should also contain a glossary for all important concepts. Commonly Accepted Best Practices. It makes JavaScript mstacode cleaner language see Strict Mode. Avoid the pitfalls of automatic semicolon insertion see Automatic Semicolon Insertion.

You can write string literals with either single quotes or double quotes in JavaScript.