A function in JavaScript is an object, because,
- Functions contain properties like objects
- We can add new properties or read the properties
- We can pass a function to another function along with its properties and data
- We can return a function along with its properties and data
- It belongs to the JavaScript prototype chain
Talk is cheap, show me your code
Let's see these statements in action,
Functions contain property
We can get a function name just like object properties,
function getBestRockBandInBd() {
return 'Warfaze';
}
console.log(getBestRockBandInBd.name);
Here we see, when we create a function, it has the property of name that can be printed just like object properties.
When we create a function, it internally creates an object with the following properties,
- Code (We can invoke them using
functionName())
- name (Stored the function name, not applicable for the arrow functions)
We can add new properties or read the properties
We can use the function to store property and retrieve it later,
function bestPsychedelicRockBandInBd() {
return 'Sonar Bangla Circus';
}
bestPsychedelicRockBand.foo = 'bar';
console.log(bestPsychedelicRockBand.foo);
Here we set a property foo to the function bestPsychedelicRockBand and later print it in the console.
We can pass a function to another function along with its properties and data
Let's pass a function to another function and do the execution,
function nemesis(whoIsVocal) {
console.log(whoIsVocal());
}
function showVocalName() {
console.log('Zohad');
}
nemesis(showVocalName);
We can return a function along with its properties and data
Now like an object, we will return a function from another function,
function anotherRockBand() {
return function aurthohin() {
console.log('This is Aurthohin');
}
}
const returnedFunction = anotherRockBand();
returnedFunction();
This feature power up the JavaScript closure feature.
It belongs to the JavaScript prototype chain
We know the base object Object has a property called prototype,
console.log(Object.hasOwnProperty('prototype'));
If we create a function, we can see, the function also has the property prototype,
function crypticFate() {}
console.log(crypticFate.hasOwnProperty('prototype'));
We can invoke a function using call, bind and apply. Interestingly these are not function's own property, we can verify this,
function crypticFate() {}
console.log(crypticFate.hasOwnProperty('call'));
console.log(crypticFate.hasOwnProperty('bind'));
console.log(crypticFate.hasOwnProperty('apply'));
Actually, these properties are inherited from the prototype chain and native to the base object. To verify,
function crypticFate() {}
console.log(crypticFate.__proto__.hasOwnProperty('call'));
console.log(crypticFate.__proto__.hasOwnProperty('bind'));
console.log(crypticFate.__proto__.hasOwnProperty('apply'));
Final thoughts
As we see these 5 points, mentioned above, functions are just objects in JavaScript world. Let me know your thoughts on this.
