JS hasownproperty无法正常工作，无论我做什么，它都会返回false

Question

Here is my code:

console.log("findAllInvoice Result: " + JSON.stringify(data, null, 4));
console.log("hasOwnProperty Result: " + data.hasOwnProperty("totalInvoice"));
if (data.hasOwnProperty("totalInvoice")) {
    var myTotal = data.totalInvoice;
}
console.log("invoice Sum: " + myTotal)
console.log("=====RESOLVE findAllInvoice=====")
resolve(data);

Here is the result of the console.log :

=====RESOLVE findMonthBookings=====
findAllInvoice Result: [
    {
        "totalInvoice": 48758
    }
]
hasOwnProperty Result: false
invoice Sum: 0
=====RESOLVE findAllInvoice=====

I don't get it?! How can it return false when the property is clearly there?

Answer 1

Try and change the second line to this:

console.log("hasOwnProperty Result: " + data[0].hasOwnProperty("totalInvoice"));

It needs to use data[0] instead of just data .

As you posted, findAllInvoice is an array with one element that is an object [{"totalInvoice": 48758}] . You need to call hasOwnProperty on that object instead of on the containing array.