how to filter object in javascript

1// use filter() function. Let say we have array of object.
2let arr = [
3  {name: "John", age: 30},
4  {name: "Grin", age: 10},
5  {name: "Marie", age: 50},
6];
7//Now I want an array in which person having age more than 40 is not
8//there, i.e, I want to filter it out using age property. So
9let newArr = arr.filter((person)=>(return person.age <= 40));
10//filter function expects a function if it return true then it added 
11//into new array, otherwise it is ignored. So new Array would be
12/* [
13	{name: "John", age: 30},
14  	{name: "Grin", age: 10},
15   ]
16*/

1var heroes = [
2	{name: “Batman”, franchise: “DC”},
3	{name: “Ironman”, franchise: “Marvel”},
4	{name: “Thor”, franchise: “Marvel”},
5	{name: “Superman”, franchise: “DC”}
6];
7
8var marvelHeroes =  heroes.filter(function(hero) {
9	return hero.franchise == “Marvel”;
10});
11
12// [ {name: “Ironman”, franchise: “Marvel”}, {name: “Thor”, franchise: “Marvel”} ]

1function objectFilter = (obj, predicate) => 
2    Object.keys(obj)
3          .filter( key => predicate(obj[key]) )
4          .reduce( (res, key) => (res[key] = obj[key], res), {} );
5
6// Example use:
7var scores = {
8    John: 2, Sarah: 3, Janet: 1
9};
10
11var filtered = objectFilter(scores, num => num > 1); 
12console.log(filtered);

1/** filter object by key or value */
2
3/** filter object function */
4function filterObj( obj, predicate ) {
5	var result = {}, key;
6
7	for ( key in obj ) {
8		if ( obj.hasOwnProperty( key ) && predicate( key, obj[ key ] ) ) {
9			result[ key ] = obj[ key ];
10		}
11	}
12
13	return result;
14};
15
16// example
17
18// set object
19var obj = {
20	name : 'john',
21	lastName : 'smith',
22	age : 32
23}
24
25// filter out parameters using key and value
26var filteredObj = filterObj( obj, function( key, value ) {
27	return key !== 'age' && value !== 'smith'
28});
29
30// show result
31console.log( filteredObj ); // { name: "john" }

1let newArray = array.filter(function(item) {
2  return condition;
3});

1// Our data
2const fruits = {
3  apple: {
4    qty: 300,
5    color: "green",
6    name: "apple",
7    price: 2
8  },
9  banana: {
10    qty: 130,
11    color: "yellow",
12    name: "banana",
13    price: 3
14  },
15  orange: {
16    qty: 120,
17    color: "orange",
18    name: "orange",
19    price: 1.5
20  },
21  melon: {
22    qty: 70,
23    color: "yellow",
24    name: "melon",
25    price: 5
26  }
27};
28// Now let"s create a map function
29const map = (obj, fun) =>
30  Object.entries(obj).reduce(
31    (prev, [key, value]) => ({
32      ...prev,
33      [key]: fun(key, value)
34    }),
35    {}
36  );
37// Finally let's map by color for example
38const myFruits = map(fruits, (_, fruit) => fruit.color);
39/*
40{ apple: 'green',
41  banana: 'yellow',
42  orange: 'orange',
43  melon: 'yellow' }
44/*