Coffeescript existential operator sometimes checks against undefined, but not always
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How does CoffeeScript's existential operator work?
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Why does CoffeeScript wrap class definitions in a closure?
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"is" operator behaves unexpectedly with integers
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How to check for an undefined or null variable in JavaScript?
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How can I temporarily disable the "return value might be undefined" warning?
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How to check that SObject field is present in SOQL query
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What is the difference between null and undefined in JavaScript?
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Which equals operator (== vs ===) should be used in JavaScript comparisons?
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Restricing domains for universal and existential quantifiers
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Unary operator expected
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Detecting an undefined object property
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How does function application with the $ operator curry in Haskell?
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Schrödingers MySQL table: exists, yet it does not
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Getting Coffeescript to create a local variable in a FOR loop
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Why does this JavaScript code print "undefined" on the console?
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Conditional operator in Coffeescript
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JavaScript check if variable exists (is defined/initialized)