Getting the actual key string from lodash filter

Question

I'm trying to get a list of strings from a lodash filter which uses a regex to test if it should return the key. The value of every object is true (which makes me think I should just be working on a list in the first place) but anyway, just wondering, why my filter results are the values at key as opposed to the actual string value of key?

var _ = require('lodash');

var testString = 'scss';
var re = new RegExp('' + testString + '', 'g');

var visited = {
    '/home/web/scss/pages/FrontPage.scss': true,
    '/home/web/scss/pages/OtherPage.scss': true,
    '/home/web/files/otherfile.js': true
};

var keys = _.filter(visited, function(value, key){

    if (key.match(re)) {
        console.log(key, value);
        return key
    }

});
console.log(keys);

//results
/home/web/scss/pages/FrontPage.scss true
/home/web/scss/pages/OtherPage.scss true
[ true, true ]