Lesson 6/100

Tutorials jQuery Tutorial

ID Class and Element Selectors

ID Class and Element Selectors: free step-by-step lesson with examples, common mistakes, and interview tips — part of jQuery Tutorial on Toolliyo Academy.

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jQuery Tutorial · Lesson 6 of 100

ID Class and Element Selectors

Setup & DOMEvents Effects AJAXPerf & IntegrateShip & Projects

Setup & DOM · 1 — Select · ~6 min · Setup and Selectors

What is this?

ID (#id) targets one node, class (.class) targets many, and element selectors (div, button) target by tag. Combine them for precision: $("button.primary").

Why should you care?

QueryVerse forms mix unique fields and repeated row classes — picking the right selector type keeps code short.

See it live — copy this example

Examples include the jQuery 3.7 CDN. Paste into an HTML file or use Run Example to preview.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>QueryVerse</title>
  <style>
    body { font-family: system-ui, sans-serif; margin: 1.25rem; }
    .box { padding: .75rem; border: 1px solid #ccc; border-radius: 8px; margin: .5rem 0; }
    .muted { color: #666; }
    button { margin-right: .35rem; margin-top: .35rem; }
    input, select, textarea { margin: .25rem 0; }
    table { border-collapse: collapse; width: 100%; }
    th, td { border: 1px solid #ddd; padding: .4rem .55rem; text-align: left; }
    .hidden { display: none; }
    .row-odd { background: #f7f7f7; }
    .active { font-weight: 700; }
    .toast { background: #111; color: #fff; padding: .5rem .75rem; border-radius: 6px; }
  </style>
</head>
<body>
  <h2 id="title">Orders</h2>
  <button type="button" class="primary">Export</button>
  <button type="button" class="ghost">Cancel</button>
  <p class="hint muted">Hint text</p>
  <p id="out" class="box"></p>
<script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>
<script>
$(function () {
  var idText = $('#title').text();
  var primaries = $('button.primary').length;
  var hints = $('p.hint').text();
  $('#out').text('id=' + idText + ' · primaryButtons=' + primaries + ' · hint=' + hints);
});
</script>
</body>
</html>

Run Example »

Edit the code below and click Run to see the result in Toolliyo’s live editor.

Code
Result

What happened?

  • IDs should be unique in the document.
  • Classes group similar controls.
  • Element selectors are blunt — narrow them with a parent or class.

Practice next

  1. Add a second .primary button and watch the count.
  2. Change #title text and re-run mentally.
  3. Try $("button") vs $("button.ghost").
  4. Select only inside a panel: $("#panel button.primary").
  5. Compare document.getElementById with $("#title").get(0).

Remember

#id = one node. .class = groups. Combine tag + class for clarity.

Checkout action bar

A Flipkart-style merchant console QueryVerse page has Export and Cancel sharing markup.

Outcome: button.primary is wired; ghost stays untouched.

Interview prep for this lesson

Practice these questions aloud after reading—each links to a full structured answer.

Junior Detailed
Explain JavaScript in the context of jQuery.
Short answer: JavaScript runs single-threaded with an event loop. Closures capture lexical scope; promises/async handle I/O without blocking the UI thread. Real-world example (ShopNest) On the ShopNest storefront UI, thi…
Mid Detailed
What are common mistakes teams make with Components when using jQuery?
Short answer: Interviewers want a crisp definition, a practical example from your projects, and awareness of trade-offs—not textbook dumps. Explain a bit more How to structure your answer (60–90 seconds) Define Component…
Senior Detailed
How would you debug a production issue related to State in a jQuery application?
Short answer: Interviewers want a crisp definition, a practical example from your projects, and awareness of trade-offs—not textbook dumps. Explain a bit more How to structure your answer (60–90 seconds) Define State in…
Junior Detailed
Describe a real-world scenario where Performance mattered in a jQuery project.
Short answer: Interviewers want a crisp definition, a practical example from your projects, and awareness of trade-offs—not textbook dumps. Explain a bit more How to structure your answer (60–90 seconds) Define Performan…
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jQuery Tutorial
Course syllabus

jQuery Tutorial

Setup and Selectors
DOM Updates
Events
Effects
AJAX and APIs
Traversal and Plugins
Performance and Security
App Integration
Debug and Modernize
Projects
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