A for...in loop that iterates over the properties of an object, shown below as u, only executes three times. Why? code example

Example 1: loop an object in javascript

var p = {
    "p1": "value1",
    "p2": "value2",
    "p3": "value3"
};

for (var key in p) {
    if (p.hasOwnProperty(key)) {
        console.log(key + " -> " + p[key]);
    }
}

Example 2: for in javascript

for (let i = start; i < end; i++) {

}