Every

Does an array of numbers contain only odd numbers?

We need an array of numbers:

let numbers = [12, 3, 34, 23, 4];

Procedural way

let arrayContainsAllOdd = true;

for (let i = 0; i < numbers.length; i++) {
  const number = numbers[i];
  if (number % 2 === 0) {
    arrayContainsAllOdd = false;
    break;
  }
}

console.log(arrayContainsAllOdd); // false

Functional way

We can use the every function to get a true / false value:

arrayContainsAllOdd = _.every(numbers, number => {
  return number % 2 !== 0;
});

console.log(arrayContainsAllOdd); // false

Summary

So, every returns true if all the items in the collection pass/satisfy the condition; otherwise false (even for one which doesn't).