Array.prototype.every

Determines whether all the elements of an array satisfy the specified test.

Syntax

every(predicate, thisArg?)

Parameters

• predicate function(value, index, array)

  A function that accepts value, index, and array. It is called for every element of the array until it returns a falsy value or until the end of the array.

• thisArg optional

  An object to which the this keyword is bound in the predicate function. If omitted, undefined is used as the this value.

Return value

Returns true if for all the elements of array the predicate function returned a truthy value, false otherwise.

Examples

[2, 4, 6].every(x => x % 2 == 0)

true

[2, 4, 6, 7].every(x => x % 2 == 0)

false

["moose", "monkey", "mouse"].every(s => s.startsWith("mo"))

true

["moose", "monkey", "cat"].every(s => s.startsWith("mo"))

false

function isUnique(value, index, array) {
   for (let [i, v] of array.entries()) {
      if (i != index && v == value) {
        return false
      }
   }
   return true
}

["apple", "orange", "banana"].every(isUnique)

true

["banana", "apple", "orange", "banana"].every(isUnique)

false

See also

• some