You are previewing JavaScript: The Good Parts.

JavaScript: The Good Parts

Cover of JavaScript: The Good Parts by Douglas Crockford Published by O'Reilly Media, Inc.
  1. JavaScript: The Good Parts
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. A Note Regarding Supplemental Files
    3. Preface
      1. Conventions Used in This Book
      2. Using Code Examples
      3. Safari® Books Online
      4. How to Contact Us
      5. Acknowledgments
    4. 1. Good Parts
      1. Why JavaScript?
      2. Analyzing JavaScript
      3. A Simple Testing Ground
    5. 2. Grammar
      1. Whitespace
      2. Names
      3. Numbers
      4. Strings
      5. Statements
      6. Expressions
      7. Literals
      8. Functions
    6. 3. Objects
      1. Object Literals
      2. Retrieval
      3. Update
      4. Reference
      5. Prototype
      6. Reflection
      7. Enumeration
      8. Delete
      9. Global Abatement
    7. 4. Functions
      1. Function Objects
      2. Function Literal
      3. Invocation
      4. Arguments
      5. Return
      6. Exceptions
      7. Augmenting Types
      8. Recursion
      9. Scope
      10. Closure
      11. Callbacks
      12. Module
      13. Cascade
      14. Curry
      15. Memoization
    8. 5. Inheritance
      1. Pseudoclassical
      2. Object Specifiers
      3. Prototypal
      4. Functional
      5. Parts
    9. 6. Arrays
      1. Array Literals
      2. Length
      3. Delete
      4. Enumeration
      5. Confusion
      6. Methods
      7. Dimensions
    10. 7. Regular Expressions
      1. An Example
      2. Construction
      3. Elements
    11. 8. Methods
    12. 9. Style
    13. 10. Beautiful Features
    14. A. Awful Parts
      1. Global Variables
      2. Scope
      3. Semicolon Insertion
      4. Reserved Words
      5. Unicode
      6. typeof
      7. parseInt
      8. +
      9. Floating Point
      10. NaN
      11. Phony Arrays
      12. Falsy Values
      13. hasOwnProperty
      14. Object
    15. B. Bad Parts
      1. ==
      2. with Statement
      3. eval
      4. continue Statement
      5. switch Fall Through
      6. Block-less Statements
      7. ++ −−
      8. Bitwise Operators
      9. The function Statement Versus the function Expression
      10. Typed Wrappers
      11. new
      12. void
    16. C. JSLint
      1. Undefined Variables and Functions
      2. Members
      3. Options
      4. Semicolon
      5. Line Breaking
      6. Comma
      7. Required Blocks
      8. Forbidden Blocks
      9. Expression Statements
      10. for in Statement
      11. switch Statement
      12. var Statement
      13. with Statement
      14. =
      15. == and !=
      16. Labels
      17. Unreachable Code
      18. Confusing Pluses and Minuses
      19. ++ and −−
      20. Bitwise Operators
      21. eval Is Evil
      22. void
      23. Regular Expressions
      24. Constructors and new
      25. Not Looked For
      26. HTML
      27. JSON
      28. Report
    17. D. Syntax Diagrams
    18. E. JSON
      1. JSON Syntax
      2. Using JSON Securely
      3. A JSON Parser
    19. Index
    20. About the Author
    21. Colophon
    22. SPECIAL OFFER: Upgrade this ebook with O’Reilly
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Elements

Let's look more closely at the elements that make up regular expressions.

Regexp Choice

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A regexp choice contains one or more regexp sequences. The sequences are separated by the | (vertical bar) character. The choice matches if any of the sequences match. It attempts to match each of the sequences in order. So:

"into".match(/in|int/)

matches the in in into. It wouldn't match int because the match of in was successful.

Regexp Sequence

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A regexp sequence contains one or more regexp factors. Each factor can optionally be followed by a quantifier that determines how many times the factor is allowed to appear. If there is no quantifier, then the factor will be matched one time.

Regexp Factor

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A regexp factor can be a character, a parenthesized group, a character class, or an escape sequence. All characters are treated literally except for the control characters and the special characters:

\ / [ ] ( ) { } ? + * | . ^ $

which must be escaped with a \ prefix if they are to be matched literally. When in doubt, any special character can be given a \ prefix to make it literal. The \ prefix does not make letters or digits literal.

An unescaped . matches any character except a line-ending character.

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