Find whether Value in Object exists within an array

Question

I am trying to find whether the value roomTypeFilter exists within an Object inside an array. I then want to perform conditional statements depending whether the value roomTypeFilter exists or not.

Below is my code

function includes(k) {
 for (var i = 0; i < this.length; i++) {
 if (this[i] === k || (this[i] !== this[i] && k !== k)) {
 return true;
 }
 }
 return false;
}
var dayValue = this.ui.dayConstraintList.val();
var arr = [courseTemplate.get('dayConstraints')[dayValue]];
console.log(arr);
arr.includes = includes;
console.log(arr.includes('roomTypeFilter'));

The first console.log returns an Object inside an array.

Object inside Array

The second console.log returns false, in this case as roomTypeFilter exists inside the Object I want to return 'true' but I am unsure how to do so, any help would be greatly appreciated.

• Jason P: I think you're looking for hasOwnProperty
• Jason P: jsfiddle.net/btjakgoo
• Ja9ad335h: console.log(!arr.filter(d => d.hasOwnProperty('roomTypeFilter')).length);

Answer 1

Instead of using includes, use hasOwnProperty. Take a look here for more information on the hasOwnProperty. It's pretty self-explanatory from its name - it essentially returns a boolean on whether or not the object has a property. I.e., in your case, you would use:

arr[0].hasOwnProperty('roomTypeFilter');

• mcclosa: When I try console.log(arr[0].hasOwnProperty('roomTypeFilter')); I get Uncaught TypeError: Cannot read property 'hasOwnProperty' of undefined
• Ted: Then your arr[0] must be undefined. Whichever object you would like check if it contains the function you're looking for, place that at arr[0]. The syntax is essentially object.hasOwnProperty('function/property')
• mcclosa: Ahh yes, the function this is within is called on two different circumstances, it's initially undefined, but defined in another circumstance.
• Ted: Great :) Glad i could help, if you have any further questions, let me know

Answer 2

You can use hasOwnProperty method to check if object contains roomTypeFilter property.

...
if (this[i].hasOwnProperty(k)) {
 ...
}
...

Answer 3

You could refactor your includes function to use

array.prototype.some

some() executes the callback function once for each element present in the array until it finds one where callback returns a truthy value... If such an element is found, some() immediately returns true.

Here is an example.

var arr = [
 {
 roomTypeFilter: {
 name: 'foo'
 }
 },
 ["roomTypeFilter", "foo"],
 "roomTypeFilter foo"
]
function includes(arr, k) {
 return arr.some(function(item) {
 return item === Object(item) && item.hasOwnProperty(k);
 })
}
console.log("Does arr includes roomTypeFilter ? - ", includes(arr, 'roomTypeFilter'))