javascript - How to write this line better in JS -

im having simple if statment , want verify returns having default value, if yes put on variable,for me little bit ugly(to use statement twice), there shorter/nicer way write in js?

    if (this._oin._mmet[sm].returns.defval) {         var defvalue = this._oin._mmet[sm].returns.defval; 

it doesn't make sense me. if value undefined should define variable so:

if(typeof === 'undefined')  var = 'something'; 

but in case value testing if exists define variable, doesn't make sense. so, use variable there:

var defvalue = this._oin._mmet[sm].returns.defval; 

you may check if not use if not defined so:

var defvalue = this._oin._mmet[sm].returns.defval || 'undefined';