# Coaching - Back to Basics 2
with Founders and Coders
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## Functions
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### What is a function?
Some lines of code that do a predefined task. A function may take some input and return an output.
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### Why do we use functions?
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#### Define reusable code
Declare code which can be used in many places to do similar things with different inputs to give different outputs.
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#### Modularise our code
Break our code up into sections.
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#### Help us understand our code
- Having a well named function is easier to understand than a list of statements.
- A meaningful name makes it easier to understand what the function does. A function that adds two numbers can be "addTwoNumbers".
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#### Writing a function
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```javascript=
function addTwoNumbers(num1,num2){
return num1+num2;
}
var total = addTwoNumbers(2,3)
// total is assigned the returned value
```
---
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