empty javascript

1const func = () => {};
2// Or
3const func = Function();

1// Test whether strValue is empty or is None
2if (strValue) {
3    //do something
4}
5// Test wheter strValue is empty, but not None 
6if (strValue === "") {
7    //do something
8}

1var s; // undefined
2var s = ""; // ""
3s.length // 0
4

1'use strict';
2delete Object.prototype; // throws a TypeError
3

1function sum(a, a, c) { // !!! syntax error
2  'use strict';
3  return a + a + c; // wrong if this code ran
4}
5