• Regular Functions / Function Declarations -
• Anonymous Functions / Function Expressions are just function declarations without a name. Every time you write the function keyword, anywhere in your code, giving it a name right after is optional. Omitting the name makes the function, well, anonymous.
• Arrow Functions provide lexical binding, meaning you get the control back on the value of this inside the function’s body. By getting the control back, I mean that it’s fairly easy to know which object this refers to just by looking at the code where your arrow function is defined (and not called)

Code Examples

function regular(a, b) { return a + b; }
regular(1, 2); // returns 3

var anon = function (a, b) { return a + b; };
anon(1, 2);    // outputs 3
 

var arrow = (a, b) => { return a + b; };
arrow(1, 2);   // outputs 3

var arrow = (a, b) => a + b;
arrow(1, 2);   // outputs 3

(function regular(a, b) {
	console.log(a + b);
})(1, 2);                     // outputs 3
regular(1, 2);                // ReferenceError: regular is not defined

(function (a, b) {
	console.log(a + b)
})(1, 2);                     // outputs 3

((a, b) => { 
	console.log(a + b)
})(1, 2);                     // outputs 3

var regular_response = (function regular(a, b) {
	return a + b;
})(1, 2);                     
console.log(regular_response);    // outputs 3

var anon_response = (function (a, b) {
	return a + b;
})(1, 2);
console.log(anon_response);       // outputs 3
 

var arrow_response = ((a, b) => { 
	return a + b;
})(1, 2);
console.log(arrow_response);      // outputs 3

Differences Between Them

arrow function does not do ‘this’ binding, as shown below

var user = { 
    name: "Marcus Chiu", 
    regular() {    
        console.log(this.name); // 'this' binding works here
    },
	anon: function () {
		console.log(this.name); // 'this' binding works here
	},
	arrow: () => { 
        console.log(this.name); // 'this' binding FAILS here
    },
};
 
user.regular(); // outputs 'Marcus Chiu'
user.anon();    // outputs 'Marcus Chiu'
user.arrow();   // outputs nothing