The for in statement can loop over all of the property names in an object. The enumeration will include functions and prototype properties.
var fruit = {
apple: 2,
orange: 5,
pear: 1,
},
sentence = "I have ",
quantity;
for (kind in fruit) {
quantity = fruit[kind];
sentence += quantity + " " + kind + (quantity === 1 ? "" : "s") + ", ";
}
// The following line removes the trailing coma.
sentence = sentence.substr(0, sentence.length - 2) + ".";
// I have 2 apples, 5 oranges, 1 pear.