Loop Over Array in Javascript

Question

I'm using Google Chrome's Console window to try and figure out why I'm not able to loop over an array in javascript.

I have a javascript object called moveResult that looks like this:

I'm trying to loop over the MoveParts in javascript like this:

for (var movePart in moveResult.MoveParts) {
    console.log(movePart.From);
};

I always get undefined instead of the actual value. However, If I try to access the first item explicitly I get what I want, like this:

console.log(moveResult.MoveParts[0].From);

The result of this is "b1".

Why isn't my loop working?

I've also tried a foreach:

moveResult.MoveParts.foreach(function (movePart) {
    console.log(movePart.From);
};

Answer 1

I'm trying to loop over the MoveParts in javascript like this:

for (var movePart in moveResult.MoveParts) {
    console.log(movePart.From);
};

I always get undefined instead of the actual value.

Don't use for-in to loop through arrays, that's not what it's for. for-in is for looping through object properties. This answer shows various ways to loop through arrays.

The reason your for-in didn't work is that movePart is the key, not the actual entry, so if you were using an object (not an array!) you would have used moveResult.MoveParts[movePart].From.

Your forEach version only failed because:

1. It's forEach, not foreach. Capitalization matters in JavaScript.

2. You were missing the closing ) on the function call.

The answer linked above has full examples of forEach and others, but here's how yours should have looked:

    moveResult.MoveParts.forEach(function (movePart) {
    // Capital E -----------^
        console.log(movePart.From);
    });
//   ^---- closing )