JavaScript Array every method; Through this tutorial, i am going to show you how to javaScript array.every() for check whether all the given elements in an array are satisfied the given test condition.
JavaScript Array every()
method
Javascript Array every()
method, check whether all the array elements are fulfilled the given test condition. It returns true when each given array element fulfills the test condition, otherwise return false.
In ES5, JavaScript Array every()
method, tests each element of array with specific test condition with function.
Syntax of javascript every()
method
The following represents the syntax of the every()
method; as shown below:
arrayObject.every(callback[, thisArg])
The every()
method accepts two named parameters: callback
and thisArg
. As shown below:
function callback(currentElement, index, array){ //... }
The callback()
function accepts 3 parameters:
- First, the
currentElement
is the current element of a given array. - Second, the index is the index of the current element of a given array
- Third, the
array
is the given array
Example 1 – JavaScript Determining If All Array Elements Pass a Test
The following example of javascript every()
method:
let numbers = [1, 3, 5, 7, 9]; let output = numbers.every(function (e) { return e > 0; }); console.log(output);
Output:
true
For example, you have numeric
array, see the following:
let numbers = [1, 3, 5, 7, 9];
The following javascript code satisfies specific test condition on every element of a numeric array:
let numbers = [1, 3, 5, 7, 9]; let output = true; for (let i = 0; i < numbers.length; i++) { if (numbers[i] <= 0) { output = false; break; } } console.log(output);
Output:
true
Example 2 – JavaScript Es6 Array every()
method
By using the JS ES6 arrow functions, the javascript code can be more concise and more readable:
let numbers = [3, 5, 9, 11, 15]; let result = numbers.every(e => e > 0); console.log(result); // true
Example 3 – JavaScript Array every()
method
The following example checks whether all the array elements are even numbers in it:
let numbers = [3, 5, 9, 11, 15]; let isEven = numbers.every(function (e) { return e % 2 == 0; }); console.log(isEven);
Output:
false
The following example checks whether all the array elements are odd numbers in it:
let numbers = [3, 5, 9, 11, 15]; let isOdd = numbers.every(function (e) { return Math.abs(e % 2) == 1; }); console.log(isOdd);
Output:
true
If you use the every()
method on an empty array, the method will always return true
for any condition.
See the following example:
let num = [].every(e => e > 0); // any condition console.log('num:', num);
Output:
num: true
Conclusion
In this tutorial, you have learned how to use the JavaScript Array every()
method to checks whether each element of an array and test defined condition.