JavaScript: Get an array of function property names from own enumerable properties of an object
JavaScript fundamental (ES6 Syntax): Exercise-48 with Solution
Write a JavaScript program to get an array of function property names from own (and optionally inherited) enumerable properties of an object.
- Use Object.keys(obj) to iterate over the object's own properties.
- If inherited is true, use Object.getPrototypeOf(obj) to also get the object's inherited properties.
- Use Array.prototype.filter() to keep only those properties that are functions.
- Omit the second argument, inherited, to not include inherited properties by default.
Sample Solution:
JavaScript Code:
//#Source https://bit.ly/2neWfJ2
const functions = (obj, inherited = false) =>
(inherited
? [...Object.keys(obj), ...Object.keys(Object.getPrototypeOf(obj))]
: Object.keys(obj)
).filter(key => typeof obj[key] === 'function');
function Foo() {
this.a = () => 1;
this.b = () => 2;
}
Foo.prototype.c = () => 3;
console.log(functions(new Foo()));
console.log(functions(new Foo(), true));
Sample Output:
["a","b"] ["a","b","c"]
Flowchart:

Live Demo:
See the Pen javascript-basic-exercise-1-47 by w3resource (@w3resource) on CodePen.
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JavaScript: Tips of the Day
Returns an array of n-tuples of consecutive elements
Example:
const tips_arr = (n, arr) => n > arr.length ? [] : arr.slice(n - 1).map((v, i) =>[...arr.slice(i, i + n - 1), v]); console.log(tips_arr(2, [1, 2, 3, 4, 5])); console.log(tips_arr(3, [1, 2, 3, 4, 5])); console.log(tips_arr(5, [1, 2, 3, 4]));
Output:
[[1, 2], [2, 3], [3, 4], [4, 5]] [[1, 2, 3], [2, 3, 4], [3, 4, 5]] []
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