Dynamically return specific attribute from an object

Question

I'm trying to create a function that will return the needed attribute from an object.

The object will look like this:

export var Characters = [
    {
        id: 1,
        Name: "Abe",
        HitPointValue: "124",
        StrengthValue: "12",
        IntelligenceValue: "14",
        WisdomValue: "16",
        DexterityValue: "12",
        ConstitutionValue: "10",
        CharismaValue: "17",
        Avatar: require('./images/avatar_7.jpg')
    }
]

I tried this:

export function getStat(id, stat) {
    var idx = Characters.findIndex((val) => val.id == id);
    return Characters[idx].stat;
}

For example, let's say I need to get the "WisdomValue" of this object.

So I call it like this:

        <Text style={[styles.stats]}>
            {"\n"}
            Wisdom Value: {getStat(1, 'WisdomValue')}{"\n"}
        </Text>

But I just get an error 'undefined is not an object'

How can I get just one specific attribute, but in a dynamic way? So I don't have to write a separte function like, getHitPointValue(id), get StrengthValue(id), etc...

thanks!

Mayank Shukla · Accepted Answer · 2017-05-23 16:09:38Z

2

Use [] instead of using dot notation, because you are trying to access a value by a dynamic key.

Check this snippet:

var Characters = [
    {
        id: 1,
        Name: "Abe",
        HitPointValue: "124",
        StrengthValue: "12",
        IntelligenceValue: "14",
        WisdomValue: "16",
        DexterityValue: "12",
        ConstitutionValue: "10",
        CharismaValue: "17",
    }
]

function getStat(id, stat) {
    var idx = Characters.findIndex((val) => val.id == id);
    if(idx >= 0)
       return Characters[idx][stat];
    else return "not found"
}

console.log(getStat(1, 'WisdomValue'));
console.log(getStat('15', 'abc'));

edited May 23, 2017 at 16:09

answered May 23, 2017 at 15:57

Mayank Shukla

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Comments

Freeman Lambda · Accepted Answer · 2017-05-23 16:06:55Z

var Characters = [
    {
        id: 1,
        Name: "Abe",
        HitPointValue: "124",
        StrengthValue: "12",
        IntelligenceValue: "14",
        WisdomValue: "16",
        DexterityValue: "12",
        ConstitutionValue: "10",
        CharismaValue: "17",
    }
]

function getStat(id, stat) {
    // you can directly find the object rather going through the array index
    var character = Characters.find((val) => val.id == id);
    // care for non existing characters
    if (!character) {
        throw new Error(`Character with id ${id} does not exist`);
    }
    // care for non existing stats
    if (!character.hasOwnProperty(stat)) {
        throw new Error(`Stat ${stat} is not available for character with id ${id}`);
    }
    // use the [] notation as opposed to the dot notation when evaluating dynamic property names
    return character[stat];
}

console.log(`Wisdom Value: ${getStat(1, 'WisdomValue')}`);
console.log(`Charisma Value: ${getStat(1, 'CharismaValue')}`);

try {
    console.log(getStat(2, 'Name'));
} catch (e) {
    console.log(e.message);
}

try {
    console.log(getStat(1, 'PersuasionValue'));
} catch (e) {
    console.log(e.message);
}

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