如何访问括号符号中的对象键？

Question

I can't seem to figure out how to access the spearguns object using bracket notation. I'm trying to access the "heft" key. The console log say's "undefined". Any help would be great, thanks.

var rockSpearguns = {
  Sharpshooter: {barbs: 2, weight: 10, heft: "overhand"},
  Pokepistol: {barbs: 4, weight: 8, heft: "shoulder"},
  Javelinjet: {barbs: 4, weight: 12, heft: "waist"},
  Firefork: {barbs: 6, weight: 8, heft: "overhand"},
  "The Impaler": {barbs: 1, weight: 30, heft: "chest"}
};

function listGuns(guns) {
  for (var speargun in guns) {
    // modify the log message here
    console.log("Behold! " + speargun + ", with " + this["heft"] + " heft!");
  }
}

listGuns(rockSpearguns);

Answer 1

You need to get a reference to the gun from the property name like this:

var rockSpearguns = {
                Sharpshooter: {barbs: 2, weight: 10, heft: "overhand"},
                Pokepistol: {barbs: 4, weight: 8, heft: "shoulder"},
                Javelinjet: {barbs: 4, weight: 12, heft: "waist"},
                Firefork: {barbs: 6, weight: 8, heft: "overhand"},
                "The Impaler": {barbs: 1, weight: 30, heft: "chest"}
};

function listGuns(guns) {
    for (var speargun in guns) {
        // modify the log message here
        var gun = guns[speargun];
        console.log("Behold! " + speargun + ", with " + gun["heft"] + " heft!");
    }
}

Answer 2

Here is what I ended up using:

function listGuns(guns) {
  for (var speargun in guns) {
    // modify the log message here

    console.log("Behold! " + speargun + ", with " + guns[speargun]["heft"] + " heft!");
  }