Learn ES6 The Dope Way Part III: Template Literals, Spread Operators, and Generators!

JavaScript is an essential language for any full-stack web developer to know. The language is constantly evolving, with new features and syntax being introduced in each version. One of the most significant updates to JavaScript in recent years was the release of ECMAScript 2015, also known as ES6.

ES6 introduced a ton of powerful features that make writing JavaScript faster, easier, and more fun. As a professional developer, taking the time to learn and incorporate these new capabilities into your workflow will boost your productivity and the quality of your code.

In this article, we‘ll continue our deep dive into ES6 by focusing on three key features: template literals, spread operators, and generators. By the end, you‘ll have a solid grasp of what they are, how they work, and why you should use them in your JavaScript projects. Let‘s jump in!

Why Bother Learning ES6?

Before we get into the specific features, you might be wondering – why should I even bother learning ES6? Isn‘t regular old JavaScript good enough?

Here are a few compelling reasons to embrace ES6 and level up your skills:

1. Cleaner, more readable code – ES6 introduced syntax changes, like arrow functions and template literals, that result in shorter, more concise code that‘s easier to read and understand.

2. Increased productivity – Features like destructuring assignment and default parameters reduce the amount of boilerplate code you have to write, meaning you can implement solutions faster.

3. Better performance – Some ES6 features, like the for…of loop and promises, offer performance benefits compared to their ES5 equivalents.

4. Wide browser support – As of 2020, ES6 is supported by over 95% of browsers globally, so you can confidently use its features in your web projects.

5. It‘s the future of JavaScript – ES6 laid the foundation for even more advanced features in ES2016, ES2017, and beyond. Staying up-to-date with the latest JavaScript features is key to advancing your skills and career as a web developer.

So if you‘re not already on the ES6 train, now‘s the time to hop aboard! Your future self (and your co-workers) will thank you.

Template Literals

First up, let‘s talk about template literals. This feature is an improvement on traditional string concatenation that makes it much easier to create dynamic strings.

What are Template Literals?

Template literals are a new way to define strings in JavaScript. They look just like regular strings, but instead of being wrapped in single or double quotes, they‘re wrapped in backticks (`).

Here‘s a basic example:

const myString = `This is a template literal`;

Why use Template Literals?

At first glance, template literals might not seem that special – after all, they‘re just strings. But they offer several key benefits over traditional string concatenation:

1. String Interpolation – With template literals, you can directly insert (interpolate) variables into the string without having to use the + operator or concatenation. Just wrap your variable in ${} and it will be evaluated and inserted into the string.

const name = "John";
const greeting = `Hello, ${name}!`;
console.log(greeting); // "Hello, John!"

2. Multi-line Strings – Template literals preserve newlines, so you can write multi-line strings without having to use \n or other escape characters.

const multiLineString = `
  This is a 
  multi-line string
  without any extra syntax
`;

3. Expression Interpolation – In addition to simple variables, you can also interpolate entire JavaScript expressions inside the ${} syntax. The expression will be evaluated and its result inserted into the string.

const a = 5;
const b = 10;
const result = `The sum of ${a} and ${b} is ${a + b}.`;
console.log(result); // "The sum of 5 and 10 is 15." 

These features make template literals a more concise and expressive way to create dynamic strings, compared to the traditional approach of string concatenation.

Template Literal Caveats

While template literals are awesome, there are a couple things to watch out for:

1. Escaping Backticks – If you need to use a backtick character inside your template literal, you‘ll need to escape it with a backslash:

const myString = `Here‘s a \`backtick\` character`;

2. Browser Support – While template literal support is very good across modern browsers, some older browsers like Internet Explorer don‘t support them. If you need to support older browsers, you‘ll need to transpile your code using a tool like Babel.

Spread Operator

Next up, let‘s talk about the spread operator. This simple but powerful syntax allows you to "spread out" elements of an array or object.

What is the Spread Operator?

The spread operator is represented by three dots (…) and can be used in a few different contexts:

1. Array literals – when used in an array literal, the spread operator "spreads out" the elements of one array into another.

const arr1 = [1, 2, 3];
const arr2 = [...arr1, 4, 5];
console.log(arr2); // [1, 2, 3, 4, 5]  

2. Object literals – when used in an object literal, the spread operator copies the properties of one object into another.

const obj1 = {a: 1, b: 2};
const obj2 = {...obj1, c: 3};
console.log(obj2); // {a: 1, b: 2, c: 3}

3. Function calls – when used in a function call, the spread operator "spreads out" the elements of an array into individual arguments.

const myArray = [1, 2, 3];
myFunction(...myArray); // equivalent to myFunction(1, 2, 3)

Why use the Spread Operator?

The spread operator offers a more concise and readable way to manipulate arrays and objects, compared to traditional methods. Here are a few specific benefits:

1. Simpler Array Concatenation – The spread operator makes it trivial to concatenate arrays, compared to the traditional approach of concat():

// old way
const arr1 = [1, 2];
const arr2 = [3, 4];
const concatenated = arr1.concat(arr2);

// spread operator way
const concatenated = [...arr1, ...arr2];

2. Easier Object Merging – The spread operator offers a simpler syntax for merging objects compared to Object.assign():

// old way 
const obj1 = {a: 1};
const obj2 = {b: 2};
const merged = Object.assign({}, obj1, obj2);

// spread operator way
const merged = {...obj1, ...obj2}; 

3. More Flexible Function Calls – By using the spread operator, you can pass an array of arguments to a function that expects individual arguments:

const myArray = [1, 2, 3];

// old way
myFunction.apply(null, myArray);

// spread operator way  
myFunction(...myArray);

This is especially useful for functions like Math.max() that traditionally require individual arguments:

const numbers = [23, 55, 19, 82, 41];
const maxNumber = Math.max(...numbers); // 82

Spread Operator Caveats

While the spread operator is a powerful tool, there are a few things to be aware of:

1. It‘s not a deep copy – The spread operator creates a new array or object, but it only goes one level deep. If your original array or object contains nested arrays or objects, those will be shared references, not new copies.

2. You can‘t use it everywhere – The spread operator only works with iterable objects, like arrays and strings. Trying to use it on a non-iterable object will result in an error.

3. Browser Support – While the spread operator is supported in most modern browsers, some older browsers like Internet Explorer don‘t support it. If you need to support legacy browsers, you‘ll need to transpile your code.

Generators

Last but not least, let‘s talk about generators. This is a more advanced feature that allows you to define a special type of function that can be paused and resumed.

What are Generators?

Generators are functions that can be paused and resumed at any point, allowing them to yield multiple values over time. They‘re defined using the function* syntax and use the new yield keyword to specify the points at which they should pause.

Here‘s a simple example:

function* myGenerator() {
  yield 1;
  yield 2;
  yield 3;
}

const iterator = myGenerator();

console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 2 
console.log(iterator.next().value); // 3

Each time the generator‘s next() method is called, the function runs until it encounters a yield expression, which specifies the value to be returned. The generator then pauses until next() is called again.

Why use Generators?

Generators offer a few key benefits:

1. Lazy Evaluation – Because generators can be paused, they allow you to create functions that generate values on-demand, rather than all at once. This is known as lazy evaluation and can be useful for working with large datasets or infinite sequences.

function* fibonacci() {
  let current = 0;
  let next = 1;

  while (true) {
    yield current;
    [current, next] = [next, current + next];
  }
}

const iterator = fibonacci();

console.log(iterator.next().value); // 0
console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 1
console.log(iterator.next().value); // 2
console.log(iterator.next().value); // 3

2. Simpler Asynchronous Code – Generators can be used to write asynchronous code that looks and behaves like synchronous code, making it easier to reason about.

function* fetchData() {
  const result1 = yield fetchSomething();
  const result2 = yield fetchSomethingElse(result1);
  return result2;
}

3. Defining Iterators – Generators provide a simple way to define the iteration behavior of an object. Instead of having to define a separate iterator object, you can just define a generator function.

const myIterable = {
  *[Symbol.iterator]() {
    yield 1;
    yield 2;
    yield 3;
  }
};

for (let value of myIterable) {
  console.log(value);
}

Generator Caveats

While generators are a powerful feature, they also come with a few caveats:

1. Browser Support – Generator functions are not supported in Internet Explorer or older versions of other browsers. If you need to support these browsers, you‘ll need to transpile your code.

2. Debugging – Because generator functions can be paused and resumed, debugging them can be a bit trickier than regular functions. Stepping through generator code with a debugger can sometimes cause unexpected behavior.

3. Memory Overhead – Each time you create a new generator object, it retains its own internal state. Creating many generator objects can therefore have higher memory overhead compared to regular functions.

Adoption and Usage

ES6 features like template literals, spread operators, and generators are increasingly being adopted by JavaScript developers around the world.

According to the 2020 State of JS Survey, over 90% of respondents said they have used or are interested in using template literals and spread operators in their projects. While generators had slightly lower usage at around 60%, they still ranked as one of the top ES6 features developers are keen to learn.

In terms of browser support, ES6 features are now supported by over 95% of browser share globally. This widespread support means you can feel confident using ES6 features in your production JavaScript code.

So if you‘re not already using these powerful ES6 features in your projects, now‘s a great time to start! Incorporating template literals, spread operators, and generators (where appropriate) into your code will make it more concise, expressive, and maintainable.

Conclusion

In this deep dive, we explored three powerful ES6 features that every JavaScript developer should know:

1. Template Literals – A cleaner, easier way to create dynamic strings without concatenation
2. Spread Operator – A concise syntax for copying, combining, and spreading out arrays and objects
3. Generators – Special functions that can be paused and resumed, enabling lazy evaluation and simplified async code

We looked at what they are, how they work, why you‘d use them, and some caveats to keep in mind. Hopefully you now feel empowered to start leveraging these features in your own JavaScript projects!

Remember, as a professional developer, staying up-to-date with the latest language features is key to writing clean, efficient, and maintainable code. Embracing ES6 will make you a more effective JavaScript developer and set you up for success as the language continues to evolve.

For even more ES6 learning, check out the other articles in this "ES6 The Dope Way" series:

• Part I: const, let & var
• Part II: Arrow Functions & this
• Part IV: Default Parameters, Destructuring, and a new ES6 method!
• Part V: Classes, Transpiling ES6, and More Resources!

You can also find me on Twitter where I share more JavaScript and web development tips. Feel free to reach out if you have any questions!

Now, go forth and write some dope ES6 code!