How to check if x and y are in an object?

I have an object containing some x and y positions:

var positions = [
0: {x: 720, y: 389.5},
1: {x: 736, y: 373.5},
2: {x: 736, y: 357.5},
3: {x: 720, y: 373.5},
4: {x: 736, y: 389.5},
6: {x: 720, y: 373.5},
7: {x: 752, y: 389.5},
8: {x: 704, y: 357.5},
9: {x: 752, y: 341.5},
10: {x: 720, y: 405.5},
11: {x: 704, y: 373.5},
]

In a setInterval loop, I generate new coordinates and want to check if these coordinates exists in my object in order to regenerate them until getting unexisting coordinates. Let say:

var newPosition = [720, 389.5];
// return true
var newPosition = [720, 357.5];
// return true

You could Array#some and check the properties.

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<!-- language: lang-js -->
const
addTo = array => ([x, y]) => {
if (positions.some(o => o.x === x && o.y === y)) return;
array.push({ x, y });
};

var positions = [{ x: 720, y: 389.5 }, { x: 736, y: 373.5 }, { x: 736, y: 357.5 }, { x: 720, y: 373.5 }, { x: 736, y: 389.5 }, { x: 720, y: 373.5 }, { x: 752, y: 389.5 }, { x: 704, y: 357.5 }, { x: 752, y: 341.5 }, { x: 720, y: 405.5 }, { x: 704, y: 373.5 }],
    add = addTo(positions);

add([720, 389.5]);
console.log(positions); // not added

add([720, 357.5]);
console.log(positions); // added

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The simplest solution would be:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

var positions = [{ x: 720, y: 389.5 }, { x: 736, y: 373.5 }, { x: 736, y: 357.5 }, { x: 720, y: 373.5 }, { x: 736, y: 389.5 }, { x: 720, y: 373.5 }, { x: 752, y: 389.5 }, { x: 704, y: 357.5 }, { x: 752, y: 341.5 }, { x: 720, y: 405.5 }, { x: 704, y: 373.5 }];


const adder = ([x, y]) => {
    if (!positions.find(obj => obj.x === x && obj.y === y)) {
        positions.push({x, y});
    }
};

adder([10, 20]); // was added
console.log(positions);
adder([720, 389.5]); // wasn't added
console.log(positions);

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