Pick random property from a Javascript object

Question

Suppose you have a Javascript object like {'cat':'meow','dog':'woof' ...} Is there a more concise way to pick a random property from the object than this long winded way I came up with:

function pickRandomProperty(obj) {     var prop, len = 0, randomPos, pos = 0;     for (prop in obj) {         if (obj.hasOwnProperty(prop)) {             len += 1;         }     }     randomPos = Math.floor(Math.random() * len);     for (prop in obj) {         if (obj.hasOwnProperty(prop)) {             if (pos === randomPos) {                 return prop;             }             pos += 1;         }     }        } 

Answer 1

The chosen answer will work well. However, this answer will run faster:

var randomProperty = function (obj) {     var keys = Object.keys(obj);     return obj[keys[ keys.length * Math.random() << 0]]; }; 

Answer 2

Picking a random element from a stream

function pickRandomProperty(obj) {     var result;     var count = 0;     for (var prop in obj)         if (Math.random() < 1/++count)            result = prop;     return result; }