Length of empty array in javascript -


so i'm trying 1 of basic things, , wondering what's wrong approach.

i have object containing rooms

{ rooms:     { ijxeczyu:        { id: 'ijxeczyu',         teachername: 'testteacher',         teacherid: '/#ikosyfr1ntdcpkbaaaaa',         clients: [] } },   getrooms: [function],   addroom: [function] }

now want render info table in jade. work, want extract important stuff , push array

function makearray(obj) {    var roomarray = [];    (var room in obj) {     roomarray.push({       roomid  : room.id,       teacher : room.teachername,       clients : room.clients.length || 0     })   }   return roomarray; }

pretty easy. but can't empty clients array work. typeerror: cannot read property 'length' of undefined isn't || 0part should catch?

why doesn't work? how can read length of array or 0 if there no entries?

room.clients undefined why error. reason it's undefined because room string.

a for..in loop iterates on keys of object. means room === "ijxeczyu", assuming you're passing in rooms object. access object, you'll have access object at key.

for (var name in obj) {   var room = obj[name];   ... }

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