isaacs/comma-first-var.js

## comma-first-var.js
// See comments below.

// This code sample and justification brought to you by
// Isaac Z. Schlueter, aka isaacs

// standard style
var a = "ape",
  b = "bat",
  c = "cat",
  d = "dog",
  e = "elf",
  f = "fly",
  g = "gnu",
  h = "hat",
  i = "ibu";

// comma-first style
var a = "ape"
  , b = "bat"
  , c = "cat"
  , d = "dog"
  , e = "elf"
  , f = "fly"
  , g = "gnu"
  , h = "hat"
  , i = "ibu"
  ;

// error in standard style
var a = "ape",
  b = "bat",
  c = "cat",
  d = "dog"
  e = "elf",
  f = "fly",
  g = "gnu",
  h = "hat",
  i = "ibu";

// error in comma-first style
var a = "ape"
  , b = "bat"
  , c = "cat"
  , d = "dog"
  e = "elf"
  , f = "fly"
  , g = "gnu"
  , h = "hat"
  , i = "ibu"
  ;

// Objects:

// JSON.stringify style
var o = {
    a : "ape",
    b : "bat",
    c : "cat",
    d : "dog",
    e : "elf",
    f : "fly",
    g : "gnu",
    h : "hat",
    i : "ibu"
  },
  a = [
    [ "ape", "bat" ],
    [ "cat", "dog" ],
    [ "elf", "fly" ],
    [ "gnu", "hat" ],
    [ "ibu" ]
  ];


// comma-first
var o =
    { a : "ape"
    , b : "bat"
    , c : "cat"
    , d : "dog"
    , e : "elf"
    , f : "fly"
    , g : "gnu"
    , h : "hat"
    , i : "ibu"
    }
  , a =
    [ [ "ape", "bat" ]
    , [ "cat", "dog" ]
    , [ "elf", "fly" ]
    , [ "gnu", "hat" ]
    , [ "ibu" ]
    ];

// errors in objects:

// JSON.stringify style
var o = {
    a : "ape",
    b : "bat",
    c : "cat",
    d : "dog"
    e : "elf",
    f : "fly",
    g : "gnu",
    h : "hat",
    i : "ibu"
  },
  a = [
    [ "ape", "bat" ],
    [ "cat", "dog" ],
    [ "elf", "fly" ]
    [ "gnu", "hat" ],
    [ "ibu" ]
  ];


// comma-first
var o =
    { a : "ape"
    , b : "bat"
    , c : "cat"
    , d : "dog"
    e : "elf"
    , f : "fly"
    , g : "gnu"
    , h : "hat"
    , i : "ibu"
    }
  , a =
    [ [ "ape", "bat" ]
    , [ "cat", "dog" ]
    , [ "elf", "fly" ]
    [ "gnu", "hat" ]
    , [ "ibu" ]
    ];

// Addendum: effects on the return statement.
// It does not break.

return [ 1
       , 2
       , 3
       ] // returns [1,2,3]

return { a : "ape"
       , b : "bat"
       } // returns {a:"ape",b:"bat"}

// even just separating two values by commas is fine,
// though a bit silly
return 1
     , 2
     , 3
     , 4 // returns the last value, 4

// this, however is wrong:
return
    1
  , 2 // returns undefined, because of semicolon-insertion.

// so is this. otb == fail.
return
  { a : "ape"
  , b : "bat"
  } // returns undefined,
    // then creates a block with two named statements.

// this is ok:
return ( 1
       , 2
       ) // returns 2

// so is this:
return (
  { a : "ape"
  , b : "bat"
  }
) // returns {a:"ape",b:"bat"}


// Addendum 2: A function call

doSomething( aPrettyLongVariableName
           , "A string, which has some useful information"
           , "If you put these all together, it'd be too long"
           , { a: "is for antelope", b: "is for bat" }
           , 42
           )

// Addendum 3: More realistic error in standard style:

// leaks FIVE globals!
var a = "ape eat banana",
  b = "bat, allowed to fly",
  c = "cat toy",
  d = "dog chasing the mailman,"
  e = "elf lord",
  f = "fly through the air",
  g = "gnu is not unix",
  h = "hat goes on your head",
  i = "ibu isn't a cow";

// Error: Can't call method 'forEach' of undefined.
// not passing in undefined as an argument!??
mergeLists([ apple, [ penelope, granger ] ],
           [ fun ],
           [ 1, 2, 3, 4, 5, 6, 7, 8 ]
           [ "mary's store has many pies, and cookies, and eggs," ]
           [ function() { doSomething() } ]);
	// See comments below.

	// This code sample and justification brought to you by
	// Isaac Z. Schlueter, aka isaacs

	// standard style
	var a = "ape",
	b = "bat",
	c = "cat",
	d = "dog",
	e = "elf",
	f = "fly",
	g = "gnu",
	h = "hat",
	i = "ibu";

	// comma-first style
	var a = "ape"
	, b = "bat"
	, c = "cat"
	, d = "dog"
	, e = "elf"
	, f = "fly"
	, g = "gnu"
	, h = "hat"
	, i = "ibu"
	;

	// error in standard style
	var a = "ape",
	b = "bat",
	c = "cat",
	d = "dog"
	e = "elf",
	f = "fly",
	g = "gnu",
	h = "hat",
	i = "ibu";

	// error in comma-first style
	var a = "ape"
	, b = "bat"
	, c = "cat"
	, d = "dog"
	e = "elf"
	, f = "fly"
	, g = "gnu"
	, h = "hat"
	, i = "ibu"
	;

	// Objects:

	// JSON.stringify style
	var o = {
	a : "ape",
	b : "bat",
	c : "cat",
	d : "dog",
	e : "elf",
	f : "fly",
	g : "gnu",
	h : "hat",
	i : "ibu"
	},
	a = [
	[ "ape", "bat" ],
	[ "cat", "dog" ],
	[ "elf", "fly" ],
	[ "gnu", "hat" ],
	[ "ibu" ]
	];


	// comma-first
	var o =
	{ a : "ape"
	, b : "bat"
	, c : "cat"
	, d : "dog"
	, e : "elf"
	, f : "fly"
	, g : "gnu"
	, h : "hat"
	, i : "ibu"
	}
	, a =
	[ [ "ape", "bat" ]
	, [ "cat", "dog" ]
	, [ "elf", "fly" ]
	, [ "gnu", "hat" ]
	, [ "ibu" ]
	];

	// errors in objects:

	// JSON.stringify style
	var o = {
	a : "ape",
	b : "bat",
	c : "cat",
	d : "dog"
	e : "elf",
	f : "fly",
	g : "gnu",
	h : "hat",
	i : "ibu"
	},
	a = [
	[ "ape", "bat" ],
	[ "cat", "dog" ],
	[ "elf", "fly" ]
	[ "gnu", "hat" ],
	[ "ibu" ]
	];


	// comma-first
	var o =
	{ a : "ape"
	, b : "bat"
	, c : "cat"
	, d : "dog"
	e : "elf"
	, f : "fly"
	, g : "gnu"
	, h : "hat"
	, i : "ibu"
	}
	, a =
	[ [ "ape", "bat" ]
	, [ "cat", "dog" ]
	, [ "elf", "fly" ]
	[ "gnu", "hat" ]
	, [ "ibu" ]
	];

	// Addendum: effects on the return statement.
	// It does not break.

	return [ 1
	, 2
	, 3
	] // returns [1,2,3]

	return { a : "ape"
	, b : "bat"
	} // returns {a:"ape",b:"bat"}

	// even just separating two values by commas is fine,
	// though a bit silly
	return 1
	, 2
	, 3
	, 4 // returns the last value, 4

	// this, however is wrong:
	return
	1
	, 2 // returns undefined, because of semicolon-insertion.

	// so is this. otb == fail.
	return
	{ a : "ape"
	, b : "bat"
	} // returns undefined,
	// then creates a block with two named statements.

	// this is ok:
	return ( 1
	, 2
	) // returns 2

	// so is this:
	return (
	{ a : "ape"
	, b : "bat"
	}
	) // returns {a:"ape",b:"bat"}


	// Addendum 2: A function call

	doSomething( aPrettyLongVariableName
	, "A string, which has some useful information"
	, "If you put these all together, it'd be too long"
	, { a: "is for antelope", b: "is for bat" }
	, 42
	)

	// Addendum 3: More realistic error in standard style:

	// leaks FIVE globals!
	var a = "ape eat banana",
	b = "bat, allowed to fly",
	c = "cat toy",
	d = "dog chasing the mailman,"
	e = "elf lord",
	f = "fly through the air",
	g = "gnu is not unix",
	h = "hat goes on your head",
	i = "ibu isn't a cow";

	// Error: Can't call method 'forEach' of undefined.
	// not passing in undefined as an argument!??
	mergeLists([ apple, [ penelope, granger ] ],
	[ fun ],
	[ 1, 2, 3, 4, 5, 6, 7, 8 ]
	[ "mary's store has many pies, and cookies, and eggs," ]
	[ function() { doSomething() } ]);