RubyのメソッドとJavaScriptで似たようなことをする対応【WIP】

Rubyとの比較とか

• JavaScript | MDN
• JavaScript初級者から中級者になろう — uhyohyo.net
• 文字列操作の比較表: Ruby, Python, JavaScript, Perl, C++
• 配列操作の比較表: Ruby, Python, JavaScript, Perl, C++

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String

Ruby	JavaScript
[] slice	String.prototype.charAt()
size length	String.length
to_i	Number() parseInt()
to_f	Number() parseFloat()
split	String.prototype.split()
chomp	String.prototype.trim()
chop	???

[] #slice

rb

'abc'[1] # => 'b'
'abc'.slice(1) # => 'b'

js

'abc'.charAt(1) // 'b'

String.prototype.charAt()

#size #length

rb

'abc'.size # => 3
'abc'.length # => 3

js

'abc'.length // 3

String.length

#to_i

rb

'1'.to_i # => 1
'1.1'.to_i # => 1

js

Number('1') // 1
parseInt('1') // 1
parseInt('1.1') // 1

Number
parseInt()

#to_f

rb

'1'.to_f # => 1.0
'1.1'.to_f # => 1.1

js

Number('1') // 1
parseFloat('1') // 1
parseFloat('1.1') // 1.1

Number
parseFloat()

#split

rb

'abc'.split('') # => ["a", "b", "c"]
'abc'.chars # => ["a", "b", "c"]

js

'abc'.split('') // ["a", "b", "c"]

String.prototype.split()

#chomp

rb

"\na\nb\nc\n".chomp # => "\na\nb\nc"

js

"\na\nb\nc\n".trim() // "a\nb\nc"

String.prototype.trim()

Numeric

Ruby	JavaScript
to_s	Number.prototype.toString()
ceil	Math.ceil()
floor	Math.floor()

#to_s

rb

1.to_s # => "1"
1.1.to_s # => "1.1"

js

Number('1').toString() // "1"
Number('1.1').toString() // "1.1"

Number.prototype.toString()

#ceil

rb

1.ceil # => 1
1.1.ceil # => 2

js

Math.ceil(1) // 1
Math.ceil(1.1) // 2

Math.ceil()

#floor

rb

1.floor # => 1
1.9.floor # => 1

js

Math.floor(1) // 1
Math.floor(1.9) // 1

Math.floor()

Array

Ruby	JavaScript
count size length	Array.length
join	Array.prototype.join()
sort	Array.prototype.sort()
reverse	Array.prototype.reverse()
each	Array.prototype.forEach()
map collect	Array.prototype.map()
select	Array.prototype.filter()
inject #reduce	Array.prototype.reduce()
any?	Array.prototype.some()
all?	Array.prototype.every()
include?	Array.prototype.indexOf()
include?	Array.prototype.includes()
delete	???
empty?	???
first	???
last	???
push	???
pop	???
unshift	???
shift	???
compact	???
uniq	???

#count #size #length

rb

[1, 2, 3].count # => 3
[1, 2, 3].size # => 3
[1, 2, 3].length # => 3

js

[1, 2, 3].length // 3

Array.length

#join

rb

[1, 2, 3].join('/') # => "1/2/3"

js

[1, 2, 3].join('/') // '1/2/3'

Array.prototype.join()

#sort #reverse

rb

[1, 2, 3].reverse # => [3, 2, 1]
[1, 2, 3].reverse.sort # => [1, 2, 3]

js

[1, 2, 3].reverse(); // [3, 2, 1]
[1, 2, 3].reverse().sort(); // [1, 2, 3]

Array.prototype.sort()
Array.prototype.reverse()

#each

rb

[1, 2, 3].each { |v| puts v }

js

[1,2,3].forEach(function(v) { console.log(v) });

Array.prototype.forEach()

#map #collect

rb

[1, 2, 3].map { |v| v.to_s } # => [ '1', '2', '3' ]

js

[1, 2, 3].map(function(v) { return v.toString() }); // [ '1', '2', '3' ]

Array.prototype.map()

#select

rb

[1, 2, 3].select {|v| v.odd? } # => [1, 3]

js

[1, 2, 3].filter(function(v) { return v % 2 != 0 }); // [ 1, 3 ]

Array.prototype.filter()

#inject #reduce

rb

[1, 2, 3].inject(&:+) # => 6

js

[1, 2, 3].reduce(function(r, v) { return r + v }); // 6

Array.prototype.reduce()

#any?

rb

[1, 2, 3].any? { |v| v.even? } # => true

js

[1, 2, 3].some(function(v) { return v % 2 == 0 }); // true

Array.prototype.some()

#all?

rb

[2, 4, 6].all? { |v| v.even? } # => true

js

[2, 4, 6].every(function(v) { return v % 2 == 0 }); // true

Array.prototype.every()

#include?

rb

[1, 2, 3].include?(2) # => true

js

[1, 2, 3].indexOf(2) >= 0 // true

Array.prototype.indexOf()

js

// This is an experimental technology, part of the ECMAScript 2016 (ES7) proposal.
[1, 2, 3].includes(2) // true

Array.prototype.includes()

Hash

Ruby	JavaScript
keys	Object.keys()
values	???
each	???
map	???
size	???
empty?	???
key? #has_key?	???
value? #has_value?	???

#keys

rb

{a: 1, b: 2}.keys # => [:a, :b]

js

Object.keys({a: 1, b: 2}) // [ 'a', 'b' ]

Object.keys()

Range

(1..10).to_a

[...Array(10).keys()]
// => [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]

Array.from([...Array(10).keys()], (v, i) => i + 1)
// => [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]

---

JavaScript ガイド

Statements

オブジェクト操作文

for ... in

var obj = {a: 1, b: 2};
for (var key in obj) {
  console.log(key + '=[' + obj[key] + ']');
};
// a=[1]
// b=[2]

var obj = [1, 2];
for (var idx in obj) {
  console.log(idx + '=[' + obj[idx] + ']');
};
// 0=[1]
// 1=[2]