JavaScript Dollar Sign ($) Explained: jQuery, Template Literals, and Common Pitfalls

1 1. Introduction
2 2. The Basics and Role of “$” in JavaScript
3 3. How to Use “$” in jQuery
4 4. How to Use “${}” in Template Literals
5 5. Examples of Using “$” in Other Libraries
6 6. Troubleshooting and Precautions
7 7. Frequently Asked Questions (FAQ)
8 8. Practical Examples: Using “$” in Real Projects
9 9. Conclusion

1. Introduction

The frequently used symbol “$” in JavaScript may look simple, but it can serve many purposes and is used in a wide range of scenarios. However, many developers—especially beginners—often wonder what “$” actually means and how they should use it properly.

In particular, jQuery and template literals are common places where “$” plays an important role. In this article, we’ll explain everything from the basics to more advanced usage, helping beginners and intermediate learners confidently use “$” in their code.

This article focuses on the following points:

The basic role and usage of “$” in JavaScript
Practical code examples using “$” in jQuery
Advanced examples using “${}” in template literals
How “$” is used in other libraries and frameworks
Troubleshooting and how to avoid conflicts

By reading this article, you’ll eliminate confusion around “$” and gain the ability to develop programs more efficiently. The article includes plenty of code examples, so try them out as you learn.

In the next section, we’ll take a closer look at the basic role of “$” in JavaScript.

2. The Basics and Role of “$” in JavaScript

2-1. What Is “$” in JavaScript?

“$” is a valid identifier in JavaScript (meaning it can be used as a variable name or function name), and it is not a reserved keyword. That means you can freely use it in your code.

Example 1: Using “$” in a Variable Name

const $name = "Alice";
console.log($name); // Output: Alice

Example 2: Using “$” in a Function Name

function $calculateTax(price) {
  return price * 1.1;
}
console.log($calculateTax(100)); // Output: 110

Because “$” is short and simple, it can be useful when you want to write concise code.

2-2. Why “$” Is Treated as Special

JavaScript itself does not assign any special meaning to “$”, but it became widely used for the following reasons:

The Symbol of jQuery jQuery uses “$” as its primary identifier, allowing you to write DOM operations and event handling in a very compact way. Example:

   $('#element').text('Updated text');

Variable Interpolation in Template Literals Starting with ES6, JavaScript template literals allow you to embed variables and expressions using “${}”. Example:

   const name = "Bob";
   console.log(`Hello, ${name}!`); // Output: Hello, Bob!

Usage in Other Libraries and Frameworks

In Prototype.js, “$” is used as a shortcut for DOM operations.
In AngularJS, “$” appears in dependency injection and service names.

2-3. Common Misunderstandings and Important Notes

“$” Is Not a JavaScript Reserved Word You can freely use “$” in variable and function names, but be careful because it may conflict with other libraries or frameworks.
“$” Is Not Exclusive to jQuery Although “$” is commonly used in jQuery, it does not mean jQuery is required. You can also use “$” in plain (native) JavaScript.

Example: Using “$” as a Custom Function

const $ = (id) => document.getElementById(id);
console.log($('example').innerText); // Output: text content of the element

Summary

In this section, we explained that “$” is not a special reserved keyword in JavaScript, but simply a valid identifier. Since it is often used alongside convenient features like jQuery and template literals, it’s important to understand its role correctly.

In the next section, we’ll explain how “$” is used in jQuery with practical examples.

3. How to Use “$” in jQuery

3-1. Selecting and Manipulating Elements

Example 1: Selecting Elements by ID or Class

$('#title').text('New Title');

Explanation：

$('#title'): Selects the element whose ID is title.
.text(): Changes the text inside the selected element.

Example 2: Changing Styles by Class

$('.box').addClass('active').removeClass('inactive');

Explanation：

$('.box'): Selects elements with the class box.
.addClass('active'): Adds the class active.
.removeClass('inactive'): Removes the class inactive.

3-2. Registering Events

Example: Showing an Alert When a Button Is Clicked

$('#btn').click(() => {
  alert('The button was clicked!');
});

Explanation：

.click(): Registers a click event handler.
Arrow function: Displays an alert when the button is clicked.

3-3. Working with Forms

Example 1: Getting and Setting a Text Input Value

const value = $('#text-input').val(); // Get the input value
$('#text-input').val('New value');    // Set a new value

Example 2: Checking a Checkbox State

if ($('#checkbox').prop('checked')) {
  console.log('It is checked');
} else {
  console.log('It is not checked');
}

3-4. Implementing Ajax Requests

Example 1: Fetching JSON Data

$.ajax({
  url: 'data.json',
  method: 'GET',
  success: (data) => {
    console.log(data); // Display the data in the console
  },
  error: () => {
    alert('Failed to fetch the data.');
  }
});

Explanation：

url: Specifies the request URL.
method: Specifies the HTTP method (GET or POST).
success: Runs when the data is successfully fetched.
error: Runs when the request fails.

3-5. Applying Animation Effects

Example 1: Fade In and Fade Out

$('#box').fadeIn(1000);  // Show over 1 second
$('#box').fadeOut(1000); // Hide over 1 second

Example 2: Slide Effects

$('#panel').slideDown(500); // Slide down over 0.5 seconds
$('#panel').slideUp(500);   // Slide up over 0.5 seconds

Summary

In this section, we covered the core ways “$” is used in jQuery. The key benefit is that you can implement common tasks—such as selecting and manipulating elements, registering events, handling forms, making Ajax requests, and applying animations—in a very compact way.

By using jQuery, you can write shorter JavaScript code that is often easier to read and maintain.

In the next section, we’ll explain how to use “${}” in template literals.

4. How to Use “${}” in Template Literals

4-1. Basic Syntax of Template Literals

A template literal is a string wrapped in backticks (`). By using “${}” inside the string, you can embed variables and expressions.

Example 1: Embedding a Variable

const name = "Alice";
console.log(`Hello, ${name}!`); // Output: Hello, Alice!

Example 2: Embedding a Calculation

const price = 1000;
const tax = 0.1;
console.log(`Price with tax: ${price * (1 + tax)} yen`); // Output: Price with tax: 1100 yen

4-2. Embedding More Complex Expressions

Example 1: Embedding a Conditional Expression

const isMember = true;
console.log(`Membership status: ${isMember ? 'Active' : 'Inactive'}`); // Output: Membership status: Active

Example 2: Embedding Results from Arrays or Objects

const user = { name: 'Bob', age: 25 };
console.log(`User: ${user.name}, Age: ${user.age}`); // Output: User: Bob, Age: 25

4-3. Creating Multi-line Strings

Example 1: A Message with Line Breaks

const message = `
Hello,
Let’s start learning JavaScript.
This example explains template literals.
`;
console.log(message);

4-4. Generating HTML Code

Example 1: Dynamically Generating an HTML Template

const title = 'How to Use JavaScript';
const content = 'This is an example of generating HTML with template literals.';

const html = `
  <div class="post">
    <h1>${title}</h1>
    <p>${content}</p>
  </div>
`;

console.log(html);

4-5. Nested Template Literals

Example: Dynamically Creating List Items

const items = ['Apple', 'Orange', 'Grape'];

const list = `
  <ul>
    ${items.map(item => `<li>${item}</li>`).join('')}
  </ul>
`;

console.log(list);

Summary

In this section, we explained template literals—from the basic syntax to more advanced examples. Template literals are a convenient feature that helps in many situations, including string manipulation and dynamic HTML generation.

In particular, using “${}” allows you to create flexible strings with embedded variables and expressions, improving both readability and development efficiency.

In the next section, we’ll take a look at how “$” is used in other libraries and frameworks.

5. Examples of Using “$” in Other Libraries

5-1. Using “$” in Prototype.js

Prototype.js is a JavaScript library designed to make DOM manipulation and event handling more efficient. In this library, “$” is used as a shortcut for selecting HTML elements.

Example 1: Selecting and Manipulating an Element

$('element-id').addClassName('active');

Explanation：

$('element-id'): Selects the element whose ID is element-id.
.addClassName('active'): Adds the class name active.

5-2. Using “$” in AngularJS

In AngularJS, “$” is used to identify framework-specific services and objects.

Example 1: Using the Scope Object

angular.module('app', [])
  .controller('MainCtrl', ['$scope', function($scope) {
    $scope.message = 'Hello, AngularJS!';
  }]);

Explanation：

$scope: An object that connects the view and the controller.

Example 2: Making an Ajax Request

angular.module('app', [])
  .controller('MainCtrl', ['$scope', '$http', function($scope, $http) {
    $http.get('data.json').then(response => {
      $scope.data = response.data;
    });
  }]);

5-3. Using “$” with D3.js

D3.js is a data visualization library that strongly supports selections and data binding.

Example: Combining jQuery and D3.js

$('#chart').append('<svg width="500" height="300"></svg>');
d3.select('svg')
  .append('circle')
  .attr('cx', 150)
  .attr('cy', 150)
  .attr('r', 50)
  .style('fill', 'blue');

5-4. Using “$” in React

In React, “$” itself does not have a special role, but it may still be used as part of variable names or identifiers.

Example: Using “$” as an Identifier for Styling

const $button = {
  backgroundColor: 'blue',
  color: 'white',
  padding: '10px'
};

function App() {
  return <button style={$button}>Click</button>;
}

Summary

In this section, we introduced examples of how “$” is used across libraries such as Prototype.js, AngularJS, D3.js, and React.

Prototype.js: Used as a shortcut for DOM manipulation.
AngularJS: Used for framework-specific services and scope management.
D3.js: Often combined with jQuery for efficient DOM updates.
React: Used as part of identifiers for things like style management.

In the next section, we’ll explain important precautions when using “$” and how to resolve conflicts.

6. Troubleshooting and Precautions

6-1. Conflicts Between Libraries

Common Issue 1: Conflict Between jQuery and Prototype.js

Uncaught TypeError: $ is not a function

Cause：

jQuery and Prototype.js both try to use “$”, causing one of them to fail.

Solution: Use noConflict()

var jq = jQuery.noConflict();
jq('#element').text('Conflict resolved');

6-2. Template Literal Errors

The “${}” syntax in template literals was introduced in ES6, so it is not supported in older browsers.

Error Message

SyntaxError: Unexpected token `

Solution 1: Use a Modern Browser
Modern versions of Google Chrome and Firefox work without issues.

Solution 2: Transpile Code Using Babel

Before Transpiling

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

After Transpiling

var name = "Alice";
console.log("Hello, " + name + "!");

6-3. Debugging Tips

1. Check the Current State of “$”

console.log(typeof $); // Result: 'function' or 'undefined'

function: “$” is correctly defined as a function.
undefined: “$” is not defined, or a conflict may be happening.

2. Check Dependencies

Open the browser developer tools and check the Network tab to confirm that jQuery and other libraries are being loaded correctly.

6-4. Coding Convention Notes

1. Naming Custom Functions

const $id = (id) => document.getElementById(id);
console.log($id('header').innerText);

2. Managing Scope Safely

(function($) {
  $('#element').text('Run safely');
})(jQuery);

Summary

In this section, we covered common conflict issues when using “$”, as well as template literal compatibility problems. We also introduced solutions such as noConflict(), transpiling with Babel, and debugging techniques.

In the next section, we’ll cover Frequently Asked Questions (FAQ) and explain common doubts and solutions in more detail.

7. Frequently Asked Questions (FAQ)

Q1. Is “$” required in JavaScript?

A1. No, it is not required.
In JavaScript, “$” is treated as a valid identifier, meaning you can freely use it in variable names and function names.

Example 1: Using “$” in a Regular Variable Name

const $name = "Alice";
console.log($name); // Output: Alice

Q2. Can I use “$” without using jQuery?

A2. Yes, you can.
Since “$” can be used freely as a variable or function name, you can define your own “$” function in plain JavaScript.

Example: Creating a Function to Select an Element

const $ = (selector) => document.querySelector(selector);
console.log($('p').innerText); // Gets the content of the first <p> tag

Q3. My template literal “${}” does not work. Why?

A3. Template literals were introduced in ES6, so older browsers do not support them.

Solution 1: Use a Modern Browser

Modern versions of Google Chrome and Firefox support template literals without any issues.

Solution 2: Transpile Your Code Using Babel

Example (Before Transpiling)

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

Converted code:

var name = "Alice";
console.log("Hello, " + name + "!");

Q4. “$” does not work because jQuery conflicts with another library. What should I do?

A4. You can avoid conflicts by using jQuery’s noConflict() method.

Example 1: Defining a New Identifier to Avoid Conflicts

var jq = jQuery.noConflict();
jq('#element').text('Conflict resolved');

Q5. Should I use “$” in variable names in JavaScript?

A5. There is no strict rule, but you should use it carefully.

Example: Using a Clear Name for an Identifier

const $id = (id) => document.getElementById(id);
console.log($id('header').innerText);

Q6. Are there any important points when using template literals?

A6. Yes. Pay attention to the following points.

Cases where escaping is not needed

console.log(`I'm Alice and I say "Hello!"`);

Correctly embed variables and expressions

const isMember = true;
console.log(`Status: ${isMember ? 'Active' : 'Inactive'}`);

It does not work in older browsers Template literals are an ES6 feature, so they are not supported in older browsers.

Summary

In this section, we covered common questions and solutions related to “How to use ‘$’ in JavaScript”.

In the next section, we’ll move on to practical examples and explain how “$” can be used in real-world projects.

8. Practical Examples: Using “$” in Real Projects

8-1. Building a Real-Time Search Filter

Example: Filtering a List

<input type="text" id="search" placeholder="Search...">
<ul id="list">
  <li>Apple</li>
  <li>Orange</li>
  <li>Grape</li>
  <li>Strawberry</li>
</ul>

$('#search').on('keyup', function() {
  const value = $(this).val().toLowerCase(); // Convert input to lowercase
  $('#list li').filter(function() {
    $(this).toggle($(this).text().toLowerCase().indexOf(value) > -1);
  });
});

8-2. Dark Mode Toggle

Example: Dark Mode Toggle Button

<button id="toggle-theme">Toggle Theme</button>

$('#toggle-theme').on('click', function() {
  $('body').toggleClass('dark-mode');
});

8-3. Displaying a Modal Window

Example: Modal Window Implementation

<button id="open-modal">Open Modal</button>
<div id="modal" style="display:none;">
  <div class="content">
    <p>This is a modal window.</p>
    <button id="close-modal">Close</button>
  </div>
</div>

$('#open-modal').on('click', function() {
  $('#modal').fadeIn();
});

$('#close-modal').on('click', function() {
  $('#modal').fadeOut();
});

8-4. Fetching Dynamic Data Using Ajax

Example: Loading and Displaying List Data

<ul id="user-list"></ul>
<button id="load-data">Load Data</button>

$('#load-data').on('click', function() {
  $.ajax({
    url: 'https://jsonplaceholder.typicode.com/users',
    method: 'GET',
    success: function(data) {
      $('#user-list').empty(); // Clear the list
      data.forEach(user => {
        $('#user-list').append(`<li>${user.name}</li>`);
      });
    },
    error: function() {
      alert('Failed to fetch data.');
    }
  });
});

8-5. Real-Time Form Validation

Example: Email Address Validation

<input type="email" id="email" placeholder="Email address">
<span id="error-message" style="color: red;"></span>

$('#email').on('input', function() {
  const email = $(this).val();
  const isValid = /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email);
  $('#error-message').text(isValid ? '' : 'Invalid email address.');
});

Summary

In this section, we introduced practical project examples using “$”.

These examples are useful for real-world web application development, so feel free to apply them to your own projects.

In the next section, we’ll summarize the entire article and wrap up the key takeaways about how to use “$”.

9. Conclusion

9-1. The Basic Role of “$”

A JavaScript identifier: “$” is treated as a valid identifier in JavaScript, so it can be freely used in variable names and function names.
A symbol in jQuery: In jQuery, “$” is used as a symbol that simplifies selecting and manipulating elements.
Expression embedding in template literals: In ES6 template literals, you can embed variables and expressions using “${}”.

9-2. Practical Usage

Working with jQuery

It makes it easy to select elements, register events, and apply animations.

Using template literals effectively

They are useful for dynamic string generation and embedding complex expressions.

Applying “$” in other libraries

Libraries like Prototype.js and AngularJS also use “$” as part of their own functionality.

9-3. Troubleshooting and Key Precautions

Avoiding conflicts: If “$” conflicts between libraries, you can resolve it using jQuery’s noConflict() method.
Browser compatibility: Template literals are not supported in older browsers, so using Babel to transpile your code is recommended.
Debugging tips: Use typeof $ to check whether “$” is properly defined and identify the cause of errors.

9-4. Using the Practical Examples

Through the real-world project examples, we introduced ways to use “$” effectively.

Real-time search filter: Filters a list based on user input.
Dark mode toggle: Changes the theme with a single click.
Modal window: Displays a popup-style UI dynamically.
Ajax requests: Fetches data from a server and updates the page dynamically.
Real-time validation: Validates user input immediately and displays an error message.

9-5. Next Steps

Use what you learned in this article and try writing code yourself. The following steps can help deepen your understanding:

Review the basics

Revisit simple examples using jQuery and template literals.

Customize the practical examples

Apply the filter and validation features to your own projects and improve them in your own way.

Practice troubleshooting

Intentionally create conflicts or errors and test the troubleshooting methods introduced in this article.

Final Notes

The JavaScript “$” symbol may look simple, but it is flexible and powerful. In this article, we covered everything from its basic role to practical examples.

In your future development work, apply “$” to write more efficient code and improve both readability and maintainability.

That concludes this article. Try the code examples yourself and deepen your understanding!