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// The filter function creates a new array with all elements from an original array that pass a certain functions test.

// For example, you can use the filter function to create a new array of only positive values, like below.

// The function being called takes in an argument which is the value of the current element in the array.

const nums = [-4, 3, 2, -21, 1];

const pos = nums.filter((el) => {

return el > 0

});

console.log(pos) // => [3, 2, 1]

// You can also, for example, filter out all objects in a data file that have incorrect or undefined values.

// In the example below, we filter out all elements that have an incorrect age value.

const data = [

{name: 'daniel', age: 45},

{name: 'john', age: 34},

{name: 'robert', age: null},

{name: 'jen', age: undefined},

{name: null, age: undefined}

];

// dataMod will now contain only the first two objects in the data array

const dataMod = data.filter(function(el) {

if (el.name != undefined && el.age != undefined) {

return true

}

else {

return false

}

});

console.log(dataMod)