Question

Given a dictionary-like object in Javascript such as {a:1, b:-2, c:42}, is there a simple way to randomly choose a property?

In the above example, I would like to have a function that would return a, b or c randomly.

The solution I’ve come up with is like the following:

    var proplist = []
    forEach(property in foo) {
        if(propertyIsEnumerable(foo[property]) {
            proplist.push(property);
        }
    }
    var n = proplist.length;
    // randomly choose property (randInt(n) returns a random integer in [0,n))
    proplist[randInt(n)];

Is there a more idiomatic way to do this?

Answer 1

Use Object.keys (or even Object.getOwnPropertyNames) to get a list of all properties. Then, select a random property by multiplying Math.random() with the length of the list, floored.

var propList = {}; //...
var tmpList = Object.keys(propList);
var randomPropertyName = tmpList[ Math.floor(Math.random()*tmpList.length) ];
var propertyValue = propList[randomPropertyName];