javascript - boolean operators evaluation order -


i've piece of code , can't figure out execution order:

var enabled = item.get_property('quantity') > 0 && item.get_property('unitprice') > 0 || item.get_id() === null

mozilla states here && operator has higher precendence ||, i'd expect that:

  1. is item.get_property('quantity') > 0 true? if yes, move forward
  2. is item.get_property('unitprice') > 0 true? if yes, move forward
  3. is item.get_id() === null true? if yes, return yes

but it's not way works. returns 'true' if item.get_id() === null equals true.

if have expression x b y c, x , y being operators, x having higher precedence means expression equivalent ((a x b) y c). can see, if substitute && x , || y, intrepreter evaluate && b, meaning if false shortcut false, if true check boolean value of b. if (a && b) true, interpreter shortcut true, if not, check c , return true if evaluates true.

the following table summarizes possible scenarios:

a    b    c    evaluates    result 0    0    0    a,c          0 0    0    1    a,c          1 0    1    0    a,c          0 0    1    1    a,c          1 1    0    0    a,b,c        0 1    0    1    a,b,c        1 1    1    0    a,b          1 1    1    1    a,b          1

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