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if (2) { console.log('yes') } > yes > undefined if (2==true) { console.log('yes') } > undefined I would have thought these would be the same - what's t

if (2) { console.log('yes') } > yes > undefined if (2==true) { console.log('yes') } > undefined I would have thought these would be the same - what's the difference between being "truthy" in the first case, and being ==true, as in the second?

Xophmeister 12y ago
`2` is truthy, but `==` forces a coercion, which ends up converting Boolean `true` to a number, which is 1 (`ToNumber(true) := 1` [1]), which is ostensibly not equal to 2. 1. http://www.ecma-international.org/ecma-262/5.1/#sec-9.3 http://www.ecma-international.org/ecma-262/5.1/#sec-9.3
Groxx 12y ago
I forget the specifics of Javascript, but in many languages "truthy" (used in ifs) is usually closer to "!= false" than "== true". e.g. any object or non-zero number is truthy (except "" in JS), but only a handful are actually == true or == false.
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- farnsworth 12y ago
  Good point, same in JS: if (2 != false) console.log('yes') > yes false goes to 0 and 2 != 0.
farnsworth 12y ago
Well I can answer that myself thanks to sheetjs' link to the spec. Case 1: From the section for 'if ()', http://www.ecma-international.org/ecma-262/5.1/#sec-12.5 http://www.ecma-international.org/ecma-262/5.1/#sec-12.5, If ToBoolean(GetValue(exprRef)) is true, ... new Boolean(2) => true, so 2 is 'truthy' alone inside if (). Case 2: From the == section, http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3 http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3, If Type(y) is Boolean, return the result of the comparison x == ToNumber(y). So the boolean is coerced to a number, and new Number(true) => 1. I wonder why they didn't do it the other way around, and make the number a boolean like above. You're losing seemingly useful information with new Number(<boolean>)
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Xophmeister 12y ago

`2` is truthy, but `==` forces a coercion, which ends up converting Boolean `true` to a number, which is 1 (`ToNumber(true) := 1` [1]), which is ostensibly not equal to 2. 1. http://www.ecma-international.org/ecma-262/5.1/#sec-9.3 http://www.ecma-international.org/ecma-262/5.1/#sec-9.3

Groxx 12y ago

I forget the specifics of Javascript, but in many languages "truthy" (used in ifs) is usually closer to "!= false" than "== true". e.g. any object or non-zero number is truthy (except "" in JS), but only a handful are actually == true or == false.

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farnsworth 12y ago
Good point, same in JS: if (2 != false) console.log('yes') > yes false goes to 0 and 2 != 0.

farnsworth 12y ago

Well I can answer that myself thanks to sheetjs' link to the spec. Case 1: From the section for 'if ()', http://www.ecma-international.org/ecma-262/5.1/#sec-12.5 http://www.ecma-international.org/ecma-262/5.1/#sec-12.5, If ToBoolean(GetValue(exprRef)) is true, ... new Boolean(2) => true, so 2 is 'truthy' alone inside if (). Case 2: From the == section, http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3 http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.3, If Type(y) is Boolean, return the result of the comparison x == ToNumber(y). So the boolean is coerced to a number, and new Number(true) => 1. I wonder why they didn't do it the other way around, and make the number a boolean like above. You're losing seemingly useful information with new Number(<boolean>)

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