Check if the property of a given object exists or not

Question

I'm trying to check if myObj has or not "x" properties. However, is not returning anything when myObj doesn't have the property I'm looking for. Here is the code:

var myObj = {
    gift: "pony",
    pet: "kitten",
    bed: "sleigh"
};

function checkObj(checkProp) {

    if(myObj.hasOwnProperty("gift")){
        return myObj[checkProp];
    } else if(myObj.hasOwnProperty("pet")){
        return myObj[checkProp];
    } else if(myObj.hasOwnProperty("bed")){
        return myObj[checkprop];
    } else {
        return "Not Found";
    }
}

Shidersz · Accepted Answer · 2019-02-16 16:27:40Z

3

Note: if (myObj.hasOwnProperty("gift")) will always enter because myObj has the property gift so other conditions will never be evaluated.

Don't you wanted to do just this?

var myObj = {
    gift: "pony",
    pet: "kitten",
    bed: "sleigh"
};

function checkObj(checkProp) {

    if (myObj.hasOwnProperty(checkProp)) {
        return myObj[checkProp];
    }
    else {
        return "Not Found";
    }
}

console.log(checkObj("gift"));
console.log(checkObj("foo"));

answered Feb 16, 2019 at 16:27

Shidersz

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Comments

anuragb26 · Accepted Answer · 2019-02-16 16:26:19Z

You should check the property you are passing instead of hardcoding the property in the if clauses.This could then be reduced to a ternary operator. Because if you have a variable which stores the property, use the [] notation which uses the value of the property to lookup inside your object.

If checkProp variable is 'gift' then myObj[checkProp] becomes myObj.gift as the value of the the checkProp variable is used.

function checkObj(checkProp) {
   return myObj[checkProp]?myObj[checkProp]:"Not found"
}

Amardeep Bhowmick · Accepted Answer · 2019-02-16 16:34:15Z

1

You can use Object.keys to get the list of own properties, then invoke Array.includes to look for the specific property and return it's value.

const myObj = {
    gift: "pony",
    pet: "kitten",
    bed: "sleigh"
};
function checkObj(myObj, key){
  return Object.keys(myObj).includes(key) ? myObj[key] : "Not found";
}
console.log(checkObj(myObj, 'gift'));
console.log(checkObj(myObj, 'pet'));
console.log(checkObj(myObj, 'foo'));

edited Feb 16, 2019 at 16:34

answered Feb 16, 2019 at 16:28

Amardeep Bhowmick

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Comments

jo_va · Accepted Answer · 2019-02-16 18:33:13Z

1

You can do this using the in operator to test if the specified property is in the object:

const myObj = {
    gift: "pony",
    pet: "kitten",
    bed: "sleigh"
};

function getProp(obj, prop) {
  return prop in obj ? obj[prop] : undefined;
}

console.log(getProp(myObj, 'gift'));
console.log(getProp(myObj, 'pet'));
console.log(getProp(myObj, 'bed'));
console.log(getProp(myObj, 'noProp'));

edited Feb 16, 2019 at 18:33

answered Feb 16, 2019 at 16:29

jo_va

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