Else Considered Harmful

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I F JSCONF Argentina, buenos aires, nov 29th, 2014

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J O K E

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if (eggs) { }

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W E H AV E A P RO B L E M O B V I O U S LY

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I F ?

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E L S E ?

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I N E N G L I S H B O O K S else If

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I N C O M P U T E R P R O G R A M S else If

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I N C O M P U T E R P R O G R A M S else If 2.5 times more else!

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W H Y ?

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ }

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } 1: true

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } 1: true 1: true, 2: true

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } 1: true 1: true, 2: true 1: true, 2: false

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } 1: true 1: true, 2: true 1: true, 2: false 1: true, 2: false, 3: true

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } 1: true 1: true, 2: true 1: true, 2: false 1: true, 2: false, 3: true 1: true, 2: false, 3: false

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } }

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } } 1: true

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } } 1: true 1 & 2: TRUE

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } } 1: true 1 & 2: TRUE 1 & 2 & 3: TRUE

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } } 1: true 1 & 2: TRUE 1 & 2 & 3: TRUE 1 & 2 & 3 & 4: true

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ if (⩸⩸⩸4) { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } ⩸⩸ ⩸⩸⩸⩸⩸⩸⩸⩸ } } } 1: true 1 & 2: TRUE 1 & 2 & 3: TRUE 1 & 2 & 3 & 4: true No switches, just adding :-)

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C H A N G E I S B A D

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B U I L D I N G I S G O O D

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W H Y ?

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we use complex logic: • More when we talk to computers • less when we talk to people

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P E O P L E A R E N OT G R E AT AT LO G I C

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P E O P L E A R E N OT G R E AT AT F O L LO W I N G S TAT E

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Pepole are graet at reizncinogg patetrns, but teirrlbe at foonwillg loigc.

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FA C E S P E O P L E A R E G O O D AT

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S O U N D S P E O P L E A R E G O O D AT

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https://www.ﬂickr.com/photos/fdecomite/446394032/in/photostream/

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M O R E PAT T E R N S L E S S “ E L S E ”

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N OT N E C E S S A R I LY “ D E S I G N PAT T E R N S "

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0 . E M P H A S I Z E E S S E N T I A L C O D E

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valid = validator(data) if (valid) { ⩸⩸⩸⩸⩸⩸ ⩸⩸⩸⩸⩸ ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ } else { return null; } ⩸⩸⩸⩸⩸⩸ return data;

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valid = validator(data) if (valid) { ⩸⩸⩸⩸⩸⩸ ⩸⩸⩸⩸⩸ ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ } else { return null; } ⩸⩸⩸⩸⩸⩸ return data; essential code

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valid = validator(data) if (!valid) { return null; } ⩸⩸⩸⩸⩸⩸ ⩸⩸⩸⩸⩸ ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ return data; essential code

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1 . P O LYM O R P H I S M

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G R E E K MY T H O LO GY ?

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fieldAsHtml: function(field) { if ('text' === field.type) return ; else if ('number' === field.type) return ; else if ('textarea' === field.type) return else throw new IMissYou(type, field) }

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fieldAsHtml: function(field) { if ('text' === field.type) return ; else if ('number' === field.type) return ; else if ('textarea' === field.type) return else throw new IMissYou(type, field) } fieldAsHtml: function(field) { renderer = renderers[field.type] || throw… return renderer(field) }

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Design pattern: strategy™

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refactoring: Replace Conditional with Polymorphism™

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P E O P L E ❤️ PAT T E R N S

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if ('text' === field.type) return ⩸⩸⩸⩸⩸; else if ('textarea' === field.type) return ⩸⩸⩸⩸⩸; else if ('number' === field.type) return ⩸⩸⩸⩸⩸; else if ('airplane on wheels' === field.type) return ⩸⩸⩸⩸⩸; else if ('scooter with squirrel' === field.type) return ⩸⩸⩸⩸⩸; else if ('name' === field.type && name.length > 5 return ⩸⩸⩸⩸⩸; else if ('name' === field.type && name.length < 5 return ⩸⩸⩸⩸⩸; else if ('textarea on JavaScript' === field.type) return ⩸⩸⩸⩸⩸; else if ('textarea raised with love' === field.type) return ⩸⩸⩸⩸⩸; else return ⩸⩸⩸⩸⩸;

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if ('text' === field.type) return ⩸⩸⩸⩸⩸; else if ('textarea' === field.type) return ⩸⩸⩸⩸⩸; else if ('number' === field.type) return ⩸⩸⩸⩸⩸; else if ('airplane on wheels' === field.type) return ⩸⩸⩸⩸⩸; else if ('scooter with squirrel' === field.type) return ⩸⩸⩸⩸⩸; else if ('name' === field.type && name.length > 5) return ⩸⩸⩸⩸⩸; else if ('name' === field.type && name.length < 5) return ⩸⩸⩸⩸⩸; else if ('textarea on JavaScript' === field.type) return ⩸⩸⩸⩸⩸; else if ('textarea raised with love' === field.type) return ⩸⩸⩸⩸⩸; else return ⩸⩸⩸⩸⩸;

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2 . P U T M O R E F O C U S O N A C T I O N

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if (spring) { if (weekday) { school(); } elseif (saturday) { if (raining) tv(); else football(); } else { homework(); } } else if (winter) { hibernate(); }

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if (spring) { if (weekday) { school(); } elseif (saturday) { if (raining) tv(); else football(); } else { homework(); } } else if (winter) { hibernate(); } if (spring && weekday) school(); if (spring && saturday && !raining) football(); if (spring && saturday && raining) tv(); if (spring && sunday) homework(); if (winter) hibernate();

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3 . N O E S C A P E

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E X T R A C T!

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } if (⩸⩸⩸⩸⩸1) { ⦾(⩸, ⩸⩸⩸) } else { ⩸⩸⩸ } function ⦾(⩸, ⩸⩸⩸) { ⪍ ⪍ ⪍ ⪍ ⪍ ⪍ ⪍ ⪍ }

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if (⩸⩸⩸⩸⩸1) { ⩸⩸⩸⩸ ⩸⩸⩸⩸ if (⩸⩸2) { ⩸⩸⩸⩸ } else { ⩸⩸⩸ ⩸⩸⩸⩸⩸⩸ ⩸⩸ if (⩸⩸⩸3) { ⩸⩸ } else { ⩸⩸ ⩸⩸⩸⩸⩸⩸ } } } else { ⩸⩸⩸ } var ⪍ = ⩸⩸⩸⩸⩸1; if (⪍) { ⦾(⩸, ⩸⩸⩸) } else { ⩸⩸⩸ }