How can I count text lines inside an DOM element? Can I?
JavascriptHtmlDomJavascript Problem Overview
I'm wondering if there's a way to count lines inside a div for example. Say we have a div like so:
<div id="content">hello how are you?</div>
Depending on many factors, the div can have one, or two, or even four lines of text. Is there any way for the script to know?
In other words, are automatic breaks represented in DOM at all?
Javascript Solutions
Solution 1 - Javascript
If the div's size is dependent on the content (which I assume to be the case from your description) then you can retrieve the div's height using:
var divHeight = document.getElementById('content').offsetHeight;
And divide by the font line height:
document.getElementById('content').style.lineHeight;
Or to get the line height if it hasn't been explicitly set:
var element = document.getElementById('content');
document.defaultView.getComputedStyle(element, null).getPropertyValue("lineHeight");
You will also need to take padding and inter-line spacing into account.
EDIT
Fully self-contained test, explicitly setting line-height:
function countLines() {
var el = document.getElementById('content');
var divHeight = el.offsetHeight
var lineHeight = parseInt(el.style.lineHeight);
var lines = divHeight / lineHeight;
alert("Lines: " + lines);
}
<body onload="countLines();">
<div id="content" style="width: 80px; line-height: 20px">
hello how are you? hello how are you? hello how are you? hello how are you?
</div>
</body>
Solution 2 - Javascript
Check out the function getClientRects() which can be used to count the number of lines in an element. Here is an example of how to use it.
var message_lines = $("#message_container")[0].getClientRects();
It returns a javascript DOM object. The amount of lines can be known by doing this:
var amount_of_lines = message_lines.length;
A few things to note is it only works if the containing element is inline, however you can surround the containing inline element with a block element to control the width like so:
console.log( message_container.getClientRects().length )
<div style="display:inline;" id="message_container">
..Text of the post..<br>
nice ha?
</div>
Though I don't recommend hard coding the style like that. It's just for example purposes.
Solution 3 - Javascript
One solution is to enclose every word in a span tag using script. Then if the Y dimension of a given span tag is less than that of it's immediate predecessor then a line break has occurred.
Solution 4 - Javascript
I wasnt satisfied with the answers here and on other questions. The highest rated answer doesn't take padding or border into account, and therefore obviously ignores box-sizing as well. My answer combines some techniques here and and on other threads to get a solution that works to my satisfaction.
It isnt perfect: When no numerical value was able to be retrieved for the line-height (e.g. normal or inherit), it just uses the font-size multiplied by 1.2. Perhaps someone else can suggest a reliable way to detect the pixel value in those cases.
Other than that, it has been able to correctly handle most of the styles and cases I have thrown at it.
jsFiddle for playing around and testing. Also inline below.
function countLines(target) {
var style = window.getComputedStyle(target, null);
var height = parseInt(style.getPropertyValue("height"));
var font_size = parseInt(style.getPropertyValue("font-size"));
var line_height = parseInt(style.getPropertyValue("line-height"));
var box_sizing = style.getPropertyValue("box-sizing");
if(isNaN(line_height)) line_height = font_size * 1.2;
if(box_sizing=='border-box')
{
var padding_top = parseInt(style.getPropertyValue("padding-top"));
var padding_bottom = parseInt(style.getPropertyValue("padding-bottom"));
var border_top = parseInt(style.getPropertyValue("border-top-width"));
var border_bottom = parseInt(style.getPropertyValue("border-bottom-width"));
height = height - padding_top - padding_bottom - border_top - border_bottom
}
var lines = Math.ceil(height / line_height);
alert("Lines: " + lines);
return lines;
}
countLines(document.getElementById("foo"));
div
{
padding:100px 0 10% 0;
background: pink;
box-sizing: border-box;
border:30px solid red;
}
<div id="foo">
x<br>
x<br>
x<br>
x<br>
</div>
Solution 5 - Javascript
Clone the container object and write 2 letters and calculate the height. This return the real height with all style applied, line height, etc. Now, calculate the height object / the size of a letter. In Jquery, the height excelude the padding, margin and border, it is great to calculate the real height of each line:
other = obj.clone();
other.html('a<br>b').hide().appendTo('body');
size = other.height() / 2;
other.remove();
lines = obj.height() / size;
If you use a rare font with different height of each letter, this does not works. But works with all normal fonts, like Arial, mono, comics, Verdana, etc. Test with your font.
Example:
<div id="content" style="width: 100px">hello how are you? hello how are you? hello how are you?</div>
<script type="text/javascript">
$(document).ready(function(){
calculate = function(obj){
other = obj.clone();
other.html('a<br>b').hide().appendTo('body');
size = other.height() / 2;
other.remove();
return obj.height() / size;
}
n = calculate($('#content'));
alert(n + ' lines');
});
</script>
Result: 6 Lines
Works in all browser without rare functions out of standards.
Solution 6 - Javascript
For those who use jQuery http://jsfiddle.net/EppA2/3/
function getRows(selector) {
var height = $(selector).height();
var line_height = $(selector).css('line-height');
line_height = parseFloat(line_height)
var rows = height / line_height;
return Math.round(rows);
}
Solution 7 - Javascript
I am convinced that it is impossible now. It was, though.
IE7’s implementation of getClientRects did exactly what I want. Open this page in IE8, try refreshing it varying window width, and see how number of lines in the first element changes accordingly. Here’s the key lines of the javascript from that page:
var rects = elementList[i].getClientRects();
var p = document.createElement('p');
p.appendChild(document.createTextNode('\'' + elementList[i].tagName + '\' element has ' + rects.length + ' line(s).'));
Unfortunately for me, Firefox always returns one client rectangle per element, and IE8 does the same now. (Martin Honnen’s page works today because IE renders it in IE compat view; press F12 in IE8 to play with different modes.)
This is sad. It looks like once again Firefox’s literal but worthless implementation of the spec won over Microsoft’s useful one. Or do I miss a situation where new getClientRects may help a developer?
Solution 8 - Javascript
based on GuyPaddock's answer from above, this seems to work for me
function getLinesCount(element) {
var prevLH = element.style.lineHeight;
var factor = 1000;
element.style.lineHeight = factor + 'px';
var height = element.getBoundingClientRect().height;
element.style.lineHeight = prevLH;
return Math.floor(height / factor);
}
the trick here is to increase the line-height so much that it will "swallow" any browser / OS differences in the way that they render fonts
Checked it with various stylings and different font sizes / families only thing that it doesn't take into account (since in my case it didnt matter), is the padding - which can easily be added to the solution.
Solution 9 - Javascript
No, not reliably. There are simply too many unknown variables
- What OS (different DPIs, font variations, etc...)?
- Do they have their font-size scaled up because they are practically blind?
- Heck, in webkit browsers, you can actually resize textboxes to your heart's desire.
The list goes on. Someday I hope there will be such a method of reliably accomplishing this with JavaScript, but until that day comes, your out of luck.
I hate these kinds of answers and I hope someone can prove me wrong.
Solution 10 - Javascript
You should be able to split('\n').length and get the line breaks.
update: this works on FF/Chrome but not IE.
<html>
<head>
<script src="jquery-1.3.2.min.js"></script>
<script>
$(document).ready(function() {
var arr = $("div").text().split('\n');
for (var i = 0; i < arr.length; i++)
$("div").after(i + '=' + arr[i] + '<br/>');
});
</script>
</head>
<body>
<div>One
Two
Three</div>
</body>
</html>
Solution 11 - Javascript
Following @BobBrunius 2010 suggestion I created this with jQuery. No doubt it could be improved but it may help some.
$(document).ready(function() {
alert("Number of lines: " + getTextLinesNum($("#textbox")));
});
function getTextLinesNum($element) {
var originalHtml = $element.html();
var words = originalHtml.split(" ");
var linePositions = [];
// Wrap words in spans
for (var i in words) {
words[i] = "<span>" + words[i] + "</span>";
}
// Temporarily replace element content with spans. Layout should be identical.
$element.html(words.join(" "));
// Iterate through words and collect positions of text lines
$element.children("span").each(function () {
var lp = $(this).position().top;
if (linePositions.indexOf(lp) == -1) linePositions.push(lp);
});
// Revert to original html content
$element.html(originalHtml);
// Return number of text lines
return linePositions.length;
}
#textbox {
width: 200px;
text-align: center;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<div id="textbox">Lorem ipsum dolor sit amet, consectetuer adipiscing elit,
<br>sed diam nonummy</div>
Solution 12 - Javascript
getClientRects return the client rects like this and if you want to get the lines, use the follow function like this
function getRowRects(element) {
var rects = [],
clientRects = element.getClientRects(),
len = clientRects.length,
clientRect, top, rectsLen, rect, i;
for(i=0; i<len; i++) {
has = false;
rectsLen = rects.length;
clientRect = clientRects[i];
top = clientRect.top;
while(rectsLen--) {
rect = rects[rectsLen];
if (rect.top == top) {
has = true;
break;
}
}
if(has) {
rect.right = rect.right > clientRect.right ? rect.right : clientRect.right;
rect.width = rect.right - rect.left;
}
else {
rects.push({
top: clientRect.top,
right: clientRect.right,
bottom: clientRect.bottom,
left: clientRect.left,
width: clientRect.width,
height: clientRect.height
});
}
}
return rects;
}
Solution 13 - Javascript
I found a way to calc the line number when I develop a html editor. The primary method is that:
-
In IE you can call getBoundingClientRects, it returns each line as a rectangle
-
In webkit or new standard html engine, it returns each element or node's client rectangles, in this case you can compare each rectangles, I mean each there must be a rectangle is the largest, so you can ignore those rectangles that height is smaller(if there is a rectangle's top smaller than it and bottom larger than it, the condition is true.)
so let's see the test result:
The green rectangle is the largest rectangle in each row
The red rectangle is the selection boundary
The blue rectangle is the boundary from start to selection after expanding, we see it may larger than red rectangle, so we have to check each rectangle's bottom to limit it must smaller than red rectangle's bottom.
var lineCount = "?";
var rects;
if (window.getSelection) {
//Get all client rectangles from body start to selection, count those rectangles that has the max bottom and min top
var bounding = {};
var range = window.getSelection().getRangeAt(0);//As this is the demo code, I dont check the range count
bounding = range.getBoundingClientRect();//!!!GET BOUNDING BEFORE SET START!!!
//Get bounding and fix it , when the cursor is in the last character of lineCount, it may expand to the next lineCount.
var boundingTop = bounding.top;
var boundingBottom = bounding.bottom;
var node = range.startContainer;
if (node.nodeType !== 1) {
node = node.parentNode;
}
var style = window.getComputedStyle(node);
var lineHeight = parseInt(style.lineHeight);
if (!isNaN(lineHeight)) {
boundingBottom = boundingTop + lineHeight;
}
else {
var fontSize = parseInt(style.fontSize);
if (!isNaN(fontSize)) {
boundingBottom = boundingTop + fontSize;
}
}
range = range.cloneRange();
//Now we have enougn datas to compare
range.setStart(body, 0);
rects = range.getClientRects();
lineCount = 0;
var flags = {};//Mark a flags to avoid of check some repeat lines again
for (var i = 0; i < rects.length; i++) {
var rect = rects[i];
if (rect.width === 0 && rect.height === 0) {//Ignore zero rectangles
continue;
}
if (rect.bottom > boundingBottom) {//Check if current rectangle out of the real bounding of selection
break;
}
var top = rect.top;
var bottom = rect.bottom;
if (flags[top]) {
continue;
}
flags[top] = 1;
//Check if there is no rectangle contains this rectangle in vertical direction.
var succ = true;
for (var j = 0; j < rects.length; j++) {
var rect2 = rects[j];
if (j !== i && rect2.top < top && rect2.bottom > bottom) {
succ = false;
break;
}
}
//If succ, add lineCount 1
if (succ) {
lineCount++;
}
}
}
else if (editor.document.selection) {//IN IE8 getClientRects returns each single lineCount as a rectangle
var range = body.createTextRange();
range.setEndPoint("EndToEnd", range);
rects = range.getClientRects();
lineCount = rects.length;
}
//Now we get lineCount here
Solution 14 - Javascript
Try this solution:
function calculateLineCount(element) {
var lineHeightBefore = element.css("line-height"),
boxSizing = element.css("box-sizing"),
height,
lineCount;
// Force the line height to a known value
element.css("line-height", "1px");
// Take a snapshot of the height
height = parseFloat(element.css("height"));
// Reset the line height
element.css("line-height", lineHeightBefore);
if (boxSizing == "border-box") {
// With "border-box", padding cuts into the content, so we have to subtract
// it out
var paddingTop = parseFloat(element.css("padding-top")),
paddingBottom = parseFloat(element.css("padding-bottom"));
height -= (paddingTop + paddingBottom);
}
// The height is the line count
lineCount = height;
return lineCount;
}
You can see it in action here: https://jsfiddle.net/u0r6avnt/
Try resizing the panels on the page (to make the right side of the page wider or shorter) and then run it again to see that it can reliably tell how many lines there are.
This problem is harder than it looks, but most of the difficulty comes from two sources:
-
Text rendering is too low-level in browsers to be directly queried from JavaScript. Even the CSS ::first-line pseudo-selector doesn't behave quite like other selectors do (you can't invert it, for example, to apply styling to all but the first line).
-
Context plays a big part in how you calculate the number of lines. For example, if line-height was not explicitly set in the hierarchy of the target element, you might get "normal" back as a line height. In addition, the element might be using
box-sizing: border-boxand therefore be subject to padding.
My approach minimizes #2 by taking control of the line-height directly and factoring in the box sizing method, leading to a more deterministic result.
Solution 15 - Javascript
You can compare element height and element height with line-height: 0
function lineCount(elm) {
const originalStyle = elm.getAttribute('style')
// normalize
elm.style.padding = 0
elm.style.border = 0
// measure
elm.style.lineHeight = 1
const totalHeight = elm.offsetHeight
elm.style.lineHeight = 0
const singleLineHeight = elm.scrollHeight * 2
const lineCount = Math.round(totalHeight / singleLineHeight)
// undo above style changes
elm.setAttribute('style', originalStyle)
return (isNaN(lineCount) || singleLineHeight == 0) ? 0 : lineCount
}
function printElmLineCount(elm){
console.log(
lineCount(elm)
)
}
p{ border:2em black solid ; padding:1em; line-height: 3em; }
<p contentEditable id='elm'>
one<br>
two<br>
three
</p>
<button onclick='printElmLineCount(elm)'>Get lines count</button>
Solution 16 - Javascript
In certain cases, like a link spanning over multiple rows in non justified text, you can get the row count and every coordinate of each line, when you use this:
var rectCollection = object.getClientRects();
https://developer.mozilla.org/en-US/docs/Web/API/Element/getClientRects
This works because each line would be different even so slightly. As long as they are, they are drawn as a different "rectangle" by the renderer.
Solution 17 - Javascript
You could count the number of line breaks in the
innerText, like this:
const text = anyDivElement.innerText;
const lines = text.split(/\r\n|\r|\n/).length;
Solution 18 - Javascript
Easiest way to do this is calculating line height and divide it by element height. This code works for any Kind of elements:
function getStyle(el,styleProp)
{
var x = el;
if (x.currentStyle)
var y = x.currentStyle[styleProp];
else if (window.getComputedStyle)
var y = document.defaultView.getComputedStyle(x,null).getPropertyValue(styleProp);
return y;
}
function calculateLineHeight (element) {
var lineHeight = parseInt(getStyle(element, 'line-height'), 10);
var clone;
var singleLineHeight;
var doubleLineHeight;
if (isNaN(lineHeight)) {
clone = element.cloneNode();
clone.innerHTML = '<br>';
element.appendChild(clone);
singleLineHeight = clone.offsetHeight;
clone.innerHTML = '<br><br>';
doubleLineHeight = clone.offsetHeight;
element.removeChild(clone);
lineHeight = doubleLineHeight - singleLineHeight;
}
return lineHeight;
}
function getNumlines(el){return Math.ceil(el.offsetHeight / calculateLineHeight (el))}
console.log(getNumlines(document.getElementById('g1')))
.Text{font-size: 28px;}
@media screen and (max-width: 780px) {
.Text{font-size: 50px;}
}
<div><span class="Text" id="g1" >
This code works for any Kind of elements: bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli bla blo bli </span>
</div>