For those not familiar, the Array.every() method tests a condition against all items in an array:
const fruits = ["Apple", "Banana", "Plum","Orange"]
//Is every fruit longer than 5 characters?
fruits.every(fruit => fruit.length > 5) //false
Items are not just limited to simple strings:
const people= [{name:"Alex", age:24}, {name:"Bob", age:37},
{name:"Carl", age:18}, {name:"Devon", age:77}]
//Is every person at least 18 years old
people.every(person => person.age >= 18) //true
//destructured
people.every(({age}) => age >= 18) //true
But did you know what happens with an empty array:
const toDoListItems = []
//Are all of my items complete
toDoListItems.every(item => item.done === true) //true
Well that was unexpected. Turns out that when every is called on an empty array, the result is always true: MDN - Array.every()
Be careful not to use the Array.every() method when your Array may have a length of 0.
Top comments (3)
Why? That is very intuitive and expected.
Well i guess that is just for me then. Hopefully no one else will need this information, but if they do I will direct them your way :)
oh yeah. very intuitive and expected
like saying every one of my kids is older than me. obviously true because I have 0 kids
also I like how the method 'some' doesn't work the same way. very intuitive indeed