Selection and Range

Web Development / Frontend / JavaScript DOM / Misc

The Selection and Range APIs let you work with selected text and manipulate document ranges programmatically.

The `Selection` Object

Access the user’s current selection via window.getSelection():

const selection = window.getSelection();
selection.toString()     // the selected text (as plain string)
selection.type           // "Range", "Caret", or "None"
selection.isCollapsed    // true if cursor (no selected text)
selection.rangeCount     // number of ranges (usually 0 or 1)

Demo: Reading Selection

HTML

<p id='select-demo'>Select some of this text to see what's selected. Try double-clicking words or dragging to select a range.</p>
<pre id='selection-output' style='background:#f1f5f9;padding:8px;border-radius:4px;'></pre>

JavaScript

const out = document.getElementById('selection-output');

document.addEventListener('mouseup', function() {
const sel = window.getSelection();
if (sel.type === 'Range') {
out.textContent =
'Selected:' + sel.toString() + '\\n' +
'length: ' + sel.toString().length + '\\n' +
'isCollapsed: ' + sel.isCollapsed + '\\n' +
'rangeCount: ' + sel.rangeCount;
} else {
out.textContent = 'No text selected (cursor only)';
}
});

Live Output Window

The `Range` Object

A Range represents a continuous fragment of the document. Get it from a selection:

const range = sel.getRangeAt(0); // first range (usually the only one)

Or create one directly:

const range = document.createRange();
range.setStart(startNode, startOffset);
range.setEnd(endNode, endOffset);

Range Properties

range.startContainer    // node where range starts
range.startOffset       // offset within start container
range.endContainer      // node where range ends
range.endOffset         // offset within end container
range.collapsed         // true if start === end
range.commonAncestorContainer // deepest common parent of start and end

Range Methods

range.deleteContents()          // remove selected content
range.extractContents()         // remove and return as DocumentFragment
range.cloneContents()           // clone the selected content
range.insertNode(newNode)       // insert a node at range start
range.surroundContents(surroundingNode) // wrap range in an element
range.cloneRange()              // deep copy

Demo: Working with Range

HTML

<div id='range-demo' style='padding:12px;border:2px solid #6366f1;border-radius:8px;'>
<p id='range-text'>This is a paragraph with <strong>bold</strong> and <em>italic</em> text inside.</p>
</div>
<div style='margin-top:8px;display:flex;gap:8px;flex-wrap:wrap;'>
<button id='highlight-range'>Highlight Selection</button>
<button id='delete-range'>Delete Selection</button>
<button id='wrap-range'>Wrap Selection in <u></button>
</div>
<pre id='range-log' style='background:#f1f5f9;padding:8px;border-radius:4px;'></pre>

JavaScript

const log = document.getElementById('range-log');

function getRange() {
const sel = window.getSelection();
if (!sel.rangeCount) {
log.textContent = 'No text selected — select some text first!';
return null;
}
return sel.getRangeAt(0);
}

document.getElementById('highlight-range').onclick = function() {
const range = getRange();
if (!range) return;
const span = document.createElement('span');
span.style.cssText = 'background:#fef9c3;padding:2px 4px;border-radius:3px;';
range.surroundContents(span);
log.textContent = 'Selection highlighted';
};

document.getElementById('delete-range').onclick = function() {
const range = getRange();
if (!range) return;
range.deleteContents();
log.textContent = 'Selection deleted';
};

document.getElementById('wrap-range').onclick = function() {
const range = getRange();
if (!range) return;
const u = document.createElement('u');
range.surroundContents(u);
log.textContent = 'Selection wrapped in underline';
};

Live Output Window

Creating Ranges Programmatically

You don’t need a user selection — create ranges from code:

const p = document.querySelector('p');
const range = document.createRange();

range.setStart(p.firstChild, 0);    // start at first char
range.setEnd(p.firstChild, 5);      // end at 5th char
range.toString();                   // first 5 chars

Demo: Programmatic Range

HTML

<p id='prog-p'>Hello World! This is a paragraph.</p>
<button id='extract-first5'>Extract first 5 chars</button>
<button id='bold-middle'>Bold middle word</button>
<button id='select-programmatic'>Select programmatically</button>
<pre id='prog-log' style='background:#f1f5f9;padding:8px;border-radius:4px;'></pre>

JavaScript

const p = document.getElementById('prog-p');
const log = document.getElementById('prog-log');

document.getElementById('extract-first5').onclick = function() {
const range = document.createRange();
range.setStart(p.firstChild, 0);
range.setEnd(p.firstChild, 5);
log.textContent = 'Range text:' + range.toString();
};

document.getElementById('bold-middle').onclick = function() {
const range = document.createRange();
const text = p.firstChild;
const word = 'World';
const start = text.textContent.indexOf(word);
range.setStart(text, start);
range.setEnd(text, start + word.length);
const b = document.createElement('strong');
range.surroundContents(b);
log.textContent = 'Made' + word + 'bold';
};

document.getElementById('select-programmatic').onclick = function() {
const sel = window.getSelection();
sel.removeAllRanges();
const range = document.createRange();
range.selectNodeContents(p);
sel.addRange(range);
log.textContent = 'Selected entire paragraph programmatically';
};

Live Output Window

Selection Events

document.addEventListener('selectionchange', function() {
  // fires whenever selection changes
});

Demo: Selection Change Event

HTML

<p id='selection-event-demo'>Select text here and see the event fire. <strong>Try it</strong> with different selections.</p>
<pre id='sel-event-log' style='background:#f1f5f9;padding:8px;border-radius:4px;'></pre>

JavaScript

const log = document.getElementById('sel-event-log');
let count = 0;

document.addEventListener('selectionchange', function() {
const sel = window.getSelection();
if (sel.type === 'Range') {
count++;
log.textContent = 'Selection changed #' + count + ':' + sel.toString().substring(0, 50) + (sel.toString().length > 50 ? '...' : '');
}
});

Live Output Window

`Range` vs `Selection`

Concept	What it is
`Selection`	What the user has selected (can have multiple ranges)
`Range`	A continuous document fragment (building block of selection)

A selection contains a range. Most of the time there’s one range per selection.

Practical: Highlight Search Terms

Demo: Search Highlight

HTML

<div id='search-demo'>
<input id='search-term' type='text' placeholder='Search term' style='padding:8px;border:1px solid #cbd5e1;border-radius:4px;'>
<button id='search-btn'>Highlight</button>
<button id='clear-highlights'>Clear</button>
<div id='search-text' style='margin-top:8px;padding:12px;background:#f8fafc;border-radius:8px;border:1px solid #e2e8f0;'>
The Document Object Model (DOM) is a programming interface for web documents. It represents the page so that programs can change the document structure, style, and content. The DOM represents the document as nodes and objects.
</div>
<pre id='search-log' style='background:#f1f5f9;padding:8px;border-radius:4px;'></pre>
</div>

JavaScript

const searchInput = document.getElementById('search-term');
const container = document.getElementById('search-text');
const log = document.getElementById('search-log');

document.getElementById('search-btn').onclick = function() {
const term = searchInput.value.trim().toLowerCase();
if (!term) return;

// Get original text (remove old highlights first)
const original = container.textContent;
container.innerHTML = '';

// Walk and wrap matches
const parts = original.split(new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\\\]/g, '\\\\$&') + ')', 'gi'));
parts.forEach(part => {
if (part.toLowerCase() === term) {
const mark = document.createElement('mark');
mark.style.cssText = 'background:#fef9c3;padding:2px 4px;border-radius:3px;';
mark.textContent = part;
container.appendChild(mark);
} else {
container.appendChild(document.createTextNode(part));
}
});
log.textContent = 'Found and highlighted ' + Math.floor(parts.length / 2) + ' occurrences of' + term;
};

document.getElementById('clear-highlights').onclick = function() {
container.innerHTML = container.textContent;
log.textContent = 'Highlights cleared';
};

Live Output Window

Key Takeaways

window.getSelection() gets the user’s selection
A Range is a document fragment defined by start and end points
setStart(node, offset) and setEnd(node, offset) define a range
range.surroundContents(element) wraps the range in an element
range.deleteContents() and range.extractContents() remove content
Use selectionchange event on document to track selection changes
Create ranges programmatically to manipulate document sections without user selection