Javascript Interview Question: Invoke a function without parenthesis

Exploring Unconventional JavaScript Calls: Mastering the Art of Invoking Functions Without Parentheses

A few years ago, I was posed with this question during an interview. Initially, I was perplexed — how could one call a function without using parentheses?

However, upon conducting further research, I discovered that the answer was surprisingly straightforward. Before delving into the various methods of calling a function, let’s explore the different ways it can be done.

First let’s see what are different ways we can call a function.

1. Direct Invocation

function show() {
  console.log('show function');
}

show();

2. Using call and apply.

function show() {
  console.log('show function');
}

show.call({});
show.apply({});

3. Using setTimeout

passing function as callback, but even in this we are using parenthesis

function show() {
  console.log('show function');
}

setTimeout(show, 0);

4. using new keyword

function show() {
  console.log('show function');
}

new show();

In all the 4 ways mentioned way we are using parenthesis.

But we have other ways to call a function which doesn’t uses parenthesis.

Solution 1

With new we can invoke a function without parentheses. The parenthesis are only required when we want to pass some default values.

function show() {
  console.log('show function');
}

new show; // logs show function

Solution 2

Using tagged template literal

function show() {
  console.log('show function');
}

show``;

Solution 3

Using getter property in object

const obj = {

    show: 1,
    get show() {
        console.log('show function');
    }
}

obj.show;

Javascript is really awesome, let me know in comments if you found it interesting.

Read my other articles:

Beyond ES6 — ES7 to ES13

JSON.stringify() traps — Javasript