Checking if a key exists in a JavaScript object?

Question

How do I check if a particular key exists in a JavaScript object or array?

If a key doesn\'t exist, and I try to access it, will it return false? Or throw an error?<

Answer 1

ES6 solution

using Array#some and Object.keys. It will return true if given key exists in the object or false if it doesn't.

var obj = {foo: 'one', bar: 'two'};
    
function isKeyInObject(obj, key) {
    var res = Object.keys(obj).some(v => v == key);
    console.log(res);
}

isKeyInObject(obj, 'foo');
isKeyInObject(obj, 'something');

One-line example.

console.log(Object.keys({foo: 'one', bar: 'two'}).some(v => v == 'foo'));