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how to solve this complex if-statement in Javascript/Jquery?
A                  B               C          D
-----------------------------------------------------------------
"external"   undefined     boolean/undefined   boolean     boolean
"wrapper"    boolean       undefined           boolean     undefined
"parent"     1             0                   1          1

// "from" is my element to check
if (
   ( typeof from.jqmData("external-page") == "undefined"
            && from.parents('body').length == 1 )
     ||
   ( typeof from.jqmData("external-page") == "boolean"
             && from.parents('body').length == 0 )
   ) {
     // do something
     }

if (from.parents('body').length === 0 || typeof from.jqmData('external-page') === 'undefined') {
    // do something
}