Determine if the object has a property and value in javascript

Use the some Array method to test your function for each value of the array:

function hasValue(obj, key, value) {
    return obj.hasOwnProperty(key) && obj[key] === value;
}
var test = [{name : "joey", age: 15}, {name: "hell", age: 12}]
console.log(test.some(function(boy) { return hasValue(boy, "age", 12); }));
// => true - there is a twelve-year-old boy in the array

Btw, don’t extend Object.prototype.