js subset of object without undefined code example

Example 1: js function pick properties from object

function pick (obj: { [key: string]: any }, props: string[] | string) {
	const propsArray = Array.isArray(props) ? props : props.split(' ')
	var picked: {
    	[key: string]: any
    } = {};
  
	propsArray.forEach(function(prop) {
		picked[prop] = obj[prop];
	});
  
	return picked
};

Example 2: javascript subset of object array matching certain property

let cities = [
    {name: 'Los Angeles', population: 3792621},
    {name: 'New York', population: 8175133},
    {name: 'Chicago', population: 2695598},
    {name: 'Houston', population: 2099451},
    {name: 'Philadelphia', population: 1526006}
];

let bigCities = cities.filter(function (e) {  // filter function
    return e.population > 3000000;
});

//Output:
[
  { name: 'Los Angeles', population: 3792621 },
  { name: 'New York', population: 8175133 }
]