underscore how to use omit

Question

How does underscore's omit work. I was expecting to remove properties with key 1 and 2 below. but it is not.

http://jsfiddle.net/FMaDq/1/

var test = {
    1: [],
    2: [],
    3: [],
    4: []
}

var out = _.omit(test, [1,2])
var out2 = _.omit(test, 1,2)
console.log(out)
console.log(out2)

Object {1: Array[0], 2: Array[0], 3: Array[0], 4: Array[0]}
Object {1: Array[0], 2: Array[0], 3: Array[0], 4: Array[0]}

Answer 1

I guess key needs to be string. This worked. http://jsfiddle.net/FMaDq/2/

var out = _.omit(test, ['1','2'])