JavaScript Array.prototype.every()

JavaScript Array.prototype.every()
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The every() method tests whether all elements in the array pass the test implemented by the provided function.

Syntax

arr.every(callback[, thisArg])

Parameters

  • callback Function to test for each element, taking three arguments:

    • currentValue (required)

      The current element being processed in the array.
      
    • index (optional)

      The index of the current element being processed in the array.
      
    • array (optional)

      The array every was called upon.
      
  • thisArg Optional. Value to use as this when executing callback.

MDN link | MSDN link

Description

The every method calls the callback function one time for each array element, in ascending index order, until the callback function returns false. If an element that causes callback to return false is found, the every method immediately returns false. Otherwise, the every method returns true.

The callback function is not called for missing elements of the array.

In addition to array objects, the every method can be used by any object that has a length property and that has numerically indexed property names. every does not mutate the array on which it is called.

Examples

function isBigEnough(element, index, array) {
  return element >= 10;
}
[12, 5, 8, 130, 44].every(isBigEnough);   // false
[12, 54, 18, 130, 44].every(isBigEnough); // true
// Define the callback function.
function CheckIfEven(value, index, ar) {
    document.write(value + " ");

    if (value % 2 == 0)
        return true;
    else
        return false;
}

// Create an array.
var numbers = [2, 4, 5, 6, 8];

// Check whether the callback function returns true for all of the
// array values.
if (numbers.every(CheckIfEven))
    document.write("All are even.");
else
    document.write("Some are not even.");

// Output:
// 2 4 5 Some are not even.

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