## Key Concepts

Review core concepts you need to learn to master this subject

### Arrow Functions (ES6)

``````.gamut-clns7e-ColorizedContainer-fontSmoothing{display:block;text-align:left;font-weight:normal;background-color:#211E2F;color:#939598;font-family:Monaco,Menlo,"Ubuntu Mono","Droid Sans Mono",Consolas,monospace;font-size:0.875rem;padding:1rem;overflow-wrap:break-word;white-space:pre-wrap;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;}// Arrow function with two arguments
const sum = (firstParam, secondParam) => {
return firstParam + secondParam;
};
console.log(sum(2,5)); // Prints: 7

// Arrow function with no arguments
const printHello = () => {
console.log('hello');
};
printHello(); // Prints: hello

// Arrow functions with a single argument
const checkWeight = weight => {
console.log(`Baggage weight : \${weight} kilograms.`);
};
checkWeight(25); // Prints: Baggage weight : 25 kilograms.

// Concise arrow functions
const multiply = (a, b) => a * b;
console.log(multiply(2, 30)); // Prints: 60 ``````

Arrow function expressions were introduced in ES6. These expressions are clean and concise. The syntax for an arrow function expression does not require the `function` keyword and uses a fat arrow `=>` to separate the parameter(s) from the body.

There are several variations of arrow functions:

• Arrow functions with a single parameter do not require `()` around the parameter list.
• Arrow functions with a single expression can use the concise function body which returns the result of the expression without the `return` keyword.
Functions
Lesson 1 of 1
1. 1
When first learning how to calculate the area of a rectangle, there’s a sequence of steps to calculate the correct answer: 1. Measure the width of the rectangle. 2. Measure the height of the rec…
2. 2
In JavaScript, there are many ways to create a function. One way to create a function is by using a function declaration. Just like how a variable declaration binds a value to a variable name, a …
3. 3
As we saw in previous exercises, a function declaration binds a function to an identifier. However, a function declaration does not ask the code inside the function body to run, it just declares …
4. 4
So far, the functions we’ve created execute a task without an input. However, some functions can take inputs and use the inputs to perform a task. When declaring a function, we can specify its _par…
5. 5
One of the features added in ES6 is the ability to use default parameters. Default parameters allow parameters to have a predetermined value in case there is no argument passed into the function …
6. 6
When a function is called, the computer will run through the function’s code and evaluate the result of calling the function. By default that resulting value is undefined. function rectangleArea(…
7. 7
We can also use the return value of a function inside another function. These functions being called within another function are often referred to as helper functions. Since each function is carr…
8. 8
Another way to define a function is to use a function expression. To define a function inside an expression, we can use the function keyword. In a function expression, the function name is usuall…
9. 9
ES6 introduced arrow function syntax, a shorter way to write functions by using the special “fat arrow” () => notation. Arrow functions remove the need to type out the keyword function every t…
10. 10
JavaScript also provides several ways to refactor arrow function syntax. The most condensed form of the function is known as concise body. We’ll explore a few of these techniques below: 1. Funct…
11. 11
Give yourself a pat on the back, you just navigated through functions! In this lesson, we covered some important concepts about functions: * A function is a reusable block of code that group…

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