Higher Order Functions

in Javascript

Javascript is weird

Higher Order Functions 

• Why?
• What?
• How?

Declarative

Tells program WHAT to do

Imperative

Tells program HOW to do 

var numbers = [1,2,3,4]
var total = 0;

for (var i = 0; i < numbers.length; i++){
  total += numbers[i]
}



​

var numbers = [1,2,3,4]

numbers.reduce(function(prev, curr) {
    return prev + curr;
}, 0);

Declarative Functions

• Reduce Side Effects
• Easier to Reason About
• More Readable Code
• Less Bugs
• Less Time

Higher Order Functions

So What is A Higher Order Function?

• Another Name for Callback Function
• A function takes another function as an argument
• Filter
• Map
• Reduce

Time to Code!