JavaScript: The Good Parts by Douglas Crockford Publisher: O ...

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Chapter 3. Objects Upon a homely object Love can wink. â William Shakespeare, The Two Gentlemen of Verona The simple types of JavaScript are numbers, strings, booleans (true and false), null, and undefined. All other values are objects. Numbers, strings, and booleans are object-like in that they have methods, but they are immutable. Objects in JavaScript are mutable keyed collections. In JavaScript, arrays are objects, functions are objects, regular expressions are objects, and, of course, objects are objects. An object is a container of properties, where a property has a name and a value. A property name can be any string, including the empty string. A property value can be any JavaScript value except for undefined. Objects in JavaScript are class-free. There is no constraint on the names of new properties or on the values of properties. Objects are useful for collecting and organizing data. Objects can contain other objects, so they can easily represent tree or graph structures. JavaScript includes a prototype linkage feature that allows one object to inherit the properties of another. When used well, this can reduce object initialization time and memory consumption. 3.1. Object Literals Object literals provide a very convenient notation for creating new object values. An object literal is a pair of curly braces surrounding zero or more name/value pairs. An object literal can appear anywhere an expression can appear: var empty_object = {}; var stooge = { "first-name": "Jerome", "last-name": "Howard" }; A property's name can be any string, including the empty string. The quotes around a property's name in an object literal are optional if the name would be a legal JavaScript name and not a reserved word. So quotes are required around "first-name", but are optional around first_name. Commas are used to separate the pairs. A property's value can be obtained from any expression, including another object literal. Objects can nest: var flight = { airline: "Oceanic", number: 815, departure: { IATA: "SYD", time: "2004-09-22 14:55", city: "Sydney" }, arrival: { IATA: "LAX", time: "2004-09-23 10:42", city: "Los Angeles" } 1 1
Page 1 and 2: JavaScript: The Good Parts by Dougl
Page 5 and 6: Section C.9. Expression Statements
Page 9 and 10: Dedication For the Lads: Clement, P
Page 11 and 12: Preface If we offend, it is with ou
Page 13 and 14: I want to thank the people I worked
Page 15 and 16: Chapter 1. Good Parts ...setting th
Page 17 and 18: Chapter 1. Good Parts ...setting th
Page 19 and 20: 1.2. Analyzing JavaScript JavaScrip
Page 21 and 22: 1.3. A Simple Testing Ground If you
Page 23 and 24: Chapter 2. Grammar I know it well:
Page 25 and 26: Chapter 2. Grammar I know it well:
Page 27 and 28: 2.2. Names A name is a letter optio
Page 29 and 30: 2.3. Numbers JavaScript has a singl
Page 31 and 32: 2.4. Strings A string literal can b
Page 33 and 34: 2.5. Statements A compilation unit
Page 35 and 36: The switch statement performs a mul
Page 37 and 38: The try statement executes a block
Page 39 and 40: 2.6. Expressions The simplest expre
Page 41 and 42: Invocation causes the execution of
Page 43 and 44: 2.7. Literals Object literals are a
Page 45: 2.8. Functions A function literal d
Page 49 and 50: Chapter 3. Objects Upon a homely ob
Page 51 and 52: 3.2. Retrieval Values can be retrie
Page 53 and 54: 3.3. Update A value in an object ca
Page 55 and 56: 3.4. Reference Objects are passed a
Page 57 and 58: 3.5. Prototype Every object is link
Page 59 and 60: 3.6. Reflection It is easy to inspe
Page 61 and 62: 3.7. Enumeration The for in stateme
Page 63 and 64: 3.8. Delete The delete operator can
Page 65 and 66: 3.9. Global Abatement JavaScript ma
Page 67 and 68: Chapter 4. Functions Why, every fau
Page 69 and 70: Chapter 4. Functions Why, every fau
Page 71 and 72: 4.2. Function Literal Function obje
Page 73 and 74: 4.3. Invocation Invoking a function
Page 75 and 76: document.writeln(myQuo.get_status(
Page 77 and 78: 4.4. Arguments A bonus parameter th
Page 79 and 80: 4.5. Return When a function is invo
Page 81 and 82: 4.6. Exceptions JavaScript provides
Page 83 and 84: 4.7. Augmenting Types JavaScript al
Page 85 and 86: 4.8. Recursion A recursive function
Page 87 and 88: 4.9. Scope Scope in a programming l
Page 89 and 90: 4.10. Closure The good news about s
Page 91 and 92: }; } } // END BAD EXAMPLE The add_t
Page 93 and 94: 4.11. Callbacks Functions can make
Page 95 and 96: 4.12. Module We can use functions a
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4.13. Cascade Some methods do not h
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4.14. Curry Functions are values, a
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4.15. Memoization Functions can use
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Chapter 5. Inheritance Divides one
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eturn s; }; Cat.prototype.get_name
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Chapter 5. Inheritance Divides one
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eturn s; }; Cat.prototype.get_name
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5.2. Object Specifiers It sometimes
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5.3. Prototypal In a purely prototy
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5.4. Functional One weakness of the
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}; for (i = 0; i < n; i += 1) { if
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5.5. Parts We can compose objects o
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Chapter 6. Arrays Thee I'll chase h
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Chapter 6. Arrays Thee I'll chase h
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6.2. Length Every array has a lengt
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6.3. Delete Since JavaScript's arra
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6.4. Enumeration Since JavaScript's
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6.5. Confusion A common error in Ja
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6.6. Methods JavaScript provides a
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6.7. Dimensions JavaScript arrays u
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Chapter 7. Regular Expressions Wher
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Regular expressions cannot be broke
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The $ represents the end of the str
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Chapter 7. Regular Expressions Wher
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Regular expressions cannot be broke
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The $ represents the end of the str
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7.2. Construction There are two way
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7.3. Elements Let's look more close
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The backslash character indicates e
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Code View: (?:!|"|#|\$|%|&|'|$|$|
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Chapter 8. Methods Though this be m
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array.slice(start, end ) The slice
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is not guaranteed to produce the co
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Function Number var a = ['a', 'b',
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Object RegExp The most common case,
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String // [3] regexp.test(string )
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it produces an array of all the mat
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is 'and' var c = text.slice(-5); //
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Chapter 9. Style Here is a silly st
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i = 0; // Set i to zero. In JavaScr
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Chapter 10. Beautiful Features Thus
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Appendix A. Awful Parts That will p
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Appendix A. Awful Parts That will p
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A.2. Scope JavaScript's syntax come
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A.3. Semicolon Insertion JavaScript
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A.4. Reserved Words The following w
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A.5. Unicode JavaScript was designe
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A.6. typeof The typeof operator ret
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A.7. parseInt parseInt is a functio
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A.8. + The + operator can add or co
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A.9. Floating Point Binary floating
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A.10. NaN The value NaN is a specia
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A.11. Phony Arrays JavaScript does
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A.12. Falsy Values JavaScript has a
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A.13. hasOwnProperty In Chapter 3,
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A.14. Object JavaScript's objects a
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Appendix B. Bad Parts And, I pray t
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Appendix B. Bad Parts And, I pray t
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B.2. with Statement JavaScript has
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B.3. eval The eval function passes
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B.4. continue Statement The continu
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B.5. switch Fall Through The switch
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B.6. Block-less Statements An if or
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B.7. ++ -- The increment and decrem
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B.8. Bitwise Operators JavaScript h
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B.9. The function Statement Versus
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B.10. Typed Wrappers JavaScript has
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B.11. new JavaScript's new operator
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B.12. void In many languages, void
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Appendix C. JSLint What error drive
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Appendix C. JSLint What error drive
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C.2. Members Since JavaScript is a
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C.3. Options The implementation of
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C.4. Semicolon JavaScript uses a C-
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C.5. Line Breaking As a further def
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C.6. Comma The comma operator can l
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C.7. Required Blocks JSLint expects
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C.8. Forbidden Blocks In many langu
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C.9. Expression Statements An expre
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C.10. for in Statement The for in s
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C.11. switch Statement A common err
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C.12. var Statement JavaScript allo
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C.13. with Statement The with state
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C.14. = JSLint does not expect to s
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C.15. == and != The == and != opera
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C.16. Labels JavaScript allows any
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C.17. Unreachable Code JSLint expec
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C.18. Confusing Pluses and Minuses
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C.19. ++ and -- The ++ (increment)
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C.20. Bitwise Operators JavaScript
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C.21. eval Is Evil The eval functio
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C.22. void In most C-like languages
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C.23. Regular Expressions Regular e
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C.24. Constructors and new Construc
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C.25. Not Looked For JSLint does no
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C.26. HTML JSLint is able to handle
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C.27. JSON JSLint can also check th
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C.28. Report If JSLint is able to c
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Appendix D. Syntax Diagrams Thou ma
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3 3
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5 5
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7 7
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9 9
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11 11
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Appendix E. JSON Farewell: the leis
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That's it. That is all of JSON. JSO
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Appendix E. JSON Farewell: the leis
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That's it. That is all of JSON. JSO
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E.2. Using JSON Securely JSON is pa
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E.3. A JSON Parser This is an imple
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}, } } error("Bad string"); white =
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} error("Syntax error"); // If ther
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Appendix. Colophon The animal on th
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Index [SYMBOL] [A] [B] [C] [D] [E]
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