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Add JS::True and JS::False #248

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Merged
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Jul 24, 2023
Merged

Add JS::True and JS::False #248

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24 changes: 24 additions & 0 deletions ext/js/lib/js.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,30 @@ module JS
Undefined = JS.eval("return undefined")
Null = JS.eval("return null")

# A boolean value in JavaScript is always a JS::Object instance from Ruby's point of view.
# If we use the boolean value returned by a JavaScript function as the condition for an if expression in Ruby,
# the if expression will always be true.
#
# == Bad Example
#
# searchParams = JS.global[:URLSearchParams].new(JS.global[:location][:search])
# if searchParams.has('phrase')
# # Always pass through here.
# ...
# else
# ...
# end
#
# Therefore, the JS::True constant is used to determine if the JavaScript function return value is true or false.
#
# == Good Example
#
# if searchParams.has('phrase') == JS::True
# ...
# end
True = JS.eval("return true;")
False = JS.eval("return false;")

class PromiseScheduler
def initialize(loop)
@loop = loop
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7 changes: 7 additions & 0 deletions packages/npm-packages/ruby-wasm-wasi/test/unit/test_js.rb
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Expand Up @@ -27,4 +27,11 @@ def test_eval
def test_try_convert
assert_nil JS.try_convert(Object.new)
end

def test_constasts
assert_equal 'null', JS::Null.to_s
assert_equal 'undefined', JS::Undefined.to_s
assert_equal 'true', JS::True.to_s
assert_equal 'false', JS::False.to_s
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If I use JS::Object with assert_equal as the argument, I get the following error:

JS::Error: TypeError: Cannot read properties of null (reading 'encoding')

To avoid the error, I compare with a string.

end
end