Functions

The Functions filter provides a large number of convenience methods Rubyists are familar with. Statements such as "252.3".to_i transform into parseInt("252.3"), or [1,3,5].yield_self { |arr| arr[1] } into (arr => arr[1])([1, 3, 5]). Generally you will want to include this filter in your configuration unless you have specific reason not to.

List of Transformations

• .abs Math.abs()
• .all? .every
• .any? .some
• .ceil Math.ceil()
• .chars Array.from()
• .chr fromCharCode
• .clear .length = 0
• .define_method klass.prototype.meth = function ...
• .delete delete target[arg]
• .downcase .toLowerCase
• .each .forEach
• .each_key for (i in ...) {}
• .each_pair for (var key in item) {var value = item[key]; ...}
• .each_value .forEach
• .each_with_index .forEach
• .end_with? .slice(-arg.length) == arg
• .empty? .length == 0
• .find_index findIndex
• .first [0]
• .first(n) .slice(0, n)
• .floor Math.floor()
• .gsub replace(//g)
• .include? .indexOf() != -1
• .index indexOf (when using arg) or findIndex (when using block)
• .inspect JSON.stringify()
• .keys() Object.keys()
• .last [*.length-1]
• .last(n) .slice(*.length-1, *.length)
• .lstrip .replace(/^\s+/, "")
• .max Math.max.apply(Math)
• .merge Object.assign({}, ...)
• .merge! Object.assign()
• .method_defined? klass.prototype.hasOwnProperty(meth) or meth in klass.prototype
• .min Math.min.apply(Math)
• .new(size,default) == .new(size).fill(default)
• .nil? == null
• .ord charCodeAt(0)
• puts console.log
• rand Math.random
• .replace .length = 0; ...push.apply(*)
• .respond_to? right in left
• .rindex .lastIndexOf
• .round Math.round()
• .rstrip .replace(/s+$/, "")
• .scan .match(//g)
• .sum .reduce(function(a, b) {a + b}, 0)
• .start_with? .substring(0, arg.length) == arg or .startsWith(arg) for ES2015+
• .upto(lim) for (var i=num; i<=lim; i+=1)
• .downto(lim) for (var i=num; i>=lim; i-=1)
• .step(lim, n).each for (var i=num; i<=lim; i+=n)
• .step(lim, -n).each for (var i=num; i>=lim; i-=n)
• (0..a).to_a Array.apply(null, {length: a}).map(Function.call, Number)
• (b..a).to_a Array.apply(null, {length: (a-b+1)}).map(Function.call, Number).map(function (idx) { return idx+b })
• (b...a).to_a Array.apply(null, {length: (a-b)}).map(Function.call, Number).map(function (idx) { return idx+b })
• .strip .trim
• .sub .replace
• .tap {|n| n} (function(n) {n; return n})(...)
• .to_f parseFloat
• .to_i parseInt
• .to_s .toString
• .to_json JSON.stringify(obj)
• .upcase .toUpperCase
• .yield_self {|n| n} (function(n) {return n})(...)
• [-n] [*.length-n] for literal values of n
• [n...m] .slice(n,m)
• [n..m] .slice(n,m+1)
• [/r/, n] .match(/r/)[n]
• [/r/, n]= .replace(/r/, ...)
• (1..2).each {|i| ...} for (var i=1 i<=2; i+=1)
• "string" * length new Array(length + 1).join("string") or "string".repeat(length) for ES2015+
• @foo.call(args) this._foo(args)
• @@foo.call(args) this.constructor._foo(args)
• Array(x) Array.prototype.slice.call(x)
• delete x delete x (note lack of parenthesis)

Additional Features

• .sub! and .gsub! become equivalent x = x.replace statements
• .map!, .reverse!, and .select! become equivalent .splice(0, .length, *.method()) statements
• setInterval and setTimeout allow block to be treated as the first parameter on the call
• for the following methods, if the block consists entirely of a simple expression (or ends with one), a return is added prior to the expression: sub, gsub, any?, all?, map, find, find_index.
• New classes subclassed off of Exception will become subclassed off of Error instead; and default constructors will be provided
• loop do...end will be replaced with while (true) {...}
• raise Exception.new(...) will be replaced with throw new Error(...)
• block_given? will check for the presence of optional argument _implicitBlockYield which is a function made accessible through the use of yield in a method body.
• alias_method works both inside of a class definition as well as called directly on a class name (e.g. MyClass.alias_method)

Additionally, there is two mappings that will only be done if explicitly included (pass include: [:class, :call] as a convert option to enable):

• .class .constructor
• a.call a()