Test all array items for equality

The .every method tests if all array elements pass a provided predicate test.

To test all objects for equality, you can use the following code snippets.

[1, 2, 1].every(function(item, i, list) { return item === list[0]; }); // false
[1, 1, 1].every(function(item, i, list) { return item === list[0]; }); // true

[1, 1, 1].every((item, i, list) => item === list[0]); // true

The following code snippets test for property equality

let data = [
  { name: "alice", id: 111 },
  { name: "alice", id: 222 }
];

data.every(function(item, i, list) { return item === list[0]; }); // false
data.every(function(item, i, list) { return item.name === list[0].name; }); // true

data.every((item, i, list) => item.name === list[0].name); // true

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