How to implement a filter() for Objects in JavaScript ?

The filter() method basically outputs all the element object that pass a specific test or satisfies a specific function. The return type of the filter() method is an array that consists of all the element(s)/object(s) satisfying the specified function. 

Syntax:

var newArray = arr.filter(callback(object[, ind[, array]])[, Arg])

Parameters:

• Callback is a predicate, to test each object of the array. Returns True to keep the object, False otherwise. It takes in three arguments:
• Object: The current object being processed in the array.
• ind (Optional): Index of the current object being processed in the array.
• array (Optional): Array on which filter was called upon.
• Arg (Optional): Value to use(.this) when executing callback.

Example 1:

javascript

var array =
    [-1, -4, 5, 6, 8, 9, -12, -5, 4, -1];
var new_array =
    array.filter(element => element >= 0);
console.log("Output: " +new_array);

Output:

Output: 5,6,8,9,4

 The above example returns all the positive elements in a given array. 

Example 2:

javascript

var employees = [
    {name: "Tony Stark", department: "IT"},
    {name: "Peter Parker", department: "Pizza Delivery"},
    {name: "Bruce Wayne", department: "IT"},
    {name: "Clark Kent", department: "Editing"}
];

var output = employees.filter(employee => employee.department == "IT");
for(var i=0;i<output.length;i++){
    console.log(output[i].name)
};

Output: 

Tony Stark
Bruce Wayne

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