The Javascript **`arr.filter()`** is used to apply a test to an array. It then returns all the values that pass this test in the form of an array.

It takes as an argument an *array* and a *function* and applies the function to each element in the array. Once done, it returns an array containing all the elements that pass the condition set by the argument function.

# Syntax
Here is the function signature for the `filter()` function in Javascript:

// function signature for the filter() method
returned_values = values.filter(function)

As described above, the `filter()` function takes two inputs.  

### Input
* **`function:`** A valid, pre-defined function. This can also be a lambda function.

* **`array:`** The array on which `filter`  function is called.

### Output
**Returned:** An array containing elements of the original array that satisfied all the conditions of the input function. 

 

# Examples

Let’s take a look at a couple of examples of how the `filter()` method works:

## 1. Using pre-defined functions

The values.filter() function is passed the function `greaterThan20()` as input parameter. 

This function checks which of the elements in the `values` array is greater than or equal to $20$. The function returns an array which is stored in the variable `filtered`.

function greaterThan20(value) {
  return value >= 20;
}

var values = [34, 19, 24, 130, 14]

var filtered = values.filter(greaterThan20);
console.log(filtered)



## 2. Using a lambda function

The values.filter() function is passed a lambda function as input parameter. 

This function checks which of the elements in the `values` array is greater than or equal to $20$. The function returns an array which is stored in the variable `filtered`.

var values = [34, 19, 24, 130, 14]

var filtered = values.filter(function(value) {
  return value >= 20;
});
console.log(filtered)

What is the JavaScript Array filter()?

The Javascript arr.filter() is used to apply a test to an array. It then returns all the values that pass this test in the form of an array. It takes as an argument an array and a function and applies the function to each element in the array. Once done, it returns an array containing all the elements that pass the condition set by the argument function. Syntax Here is the function signature for the filter() function in Javascript: 