Is there a way to style part of the text in a label - change color, boldness, size, etc?
Use HTML widget instead of Label. Then:
HTML label = new HTML();
label.setHtml("Brown <span class=\"brown\">fox</span>");
I was a little bored, and I thought I might be able to offer something useful, so, that said, I offer this:
function elemStyle(el, needle, settings) {
// if there's no 'el' or 'needle' arguments, we quit here
if (!el || !needle) {
return false;
}
else {
// if 'el' has a nodeType of 1, then it's an element node, and we can use that,
// otherwise we assume it's the id of an element, and search for that
el = el.nodeType == 1 ? el : document.getElementById(el);
// if we have a 'settings' argument and it's an object we use that,
// otherwise we create, and use, an empty object
settings = settings && typeof settings === 'object' ? settings : {};
// defining the defaults
var defaults = {
'class': 'presentation',
'elementType': 'span'
},
// get the text from the 'el':
haystack = el.textContent || el.innerText;
// iterate over the (non-prototypal) properties of the defaults
for (var prop in defaults) {
if (defaults.hasOwnProperty(prop)) {
// if the 'settings' object has that property set
// we use that, otherwise we assign the default value:
settings[prop] = settings[prop] || defaults[prop];
}
}
// defining the opening, and closing, tags (since we're using HTML
// as a string:
var open = '<' + settings.elementType + ' class="' + settings.class + '">',
close = '</' + settings.elementType + '>';
// if 'needle' is an array (which is also an object in JavaScript)
// *and* it has a length of 2 (a start, and stop, point):
if (typeof needle === 'object' && needle.length === 2) {
var start = needle[0],
stop = needle[1];
el.innerHTML = haystack.substring(0, start) + open + haystack.substring(start, stop) + close + haystack.substring(stop);
}
// otherwise if it's a string we use regular expressions:
else if (typeof needle === 'string') {
var reg = new RegExp('(' + needle + ')');
el.innerHTML = haystack.replace(reg, open + '$1' + close);
}
}
}
The above is called like so:
// a node-reference, and a string:
elemStyle(document.getElementsByTagName('label')[0], 'Input');
JS Fiddle demo.
// a node-reference, and a start-stop array:
elemStyle(document.getElementsByTagName('label')[0], [6, 8]);
JS Fiddle demo.
// an id (as a string), and a string to find, with settings:
elemStyle('label1', 'Input', {
'elementType' : 'em'
});
JS Fiddle demo.
This could definitely do with some error-catching (for example if an array is passed into the function that's less, or more, than two-elements nothing happens, and no error is returned to the user/developer; also if the el variable is neither a node-reference or an id, things go wrong: Uncaught TypeError: Cannot read property 'textContent' of null).
Having said that, I felt dirty, so I added in a simple error-check, and reporting, if the el doesn't resolve to an actual node in the document:
el = el.nodeType == 1 ? el : document.getElementById(el);
// if 'el' is null, and therefore has no value we report the error to the console
// and then quit
if (el === null) {
console.log("You need to pass in either an 'id' or a node-reference, using 'document.getElementById(\"elemID\")' or 'document.getElementsByTagName(\"elemTag\")[0].");
return false;
}
References:
document.getElementById().
JavaScript regular expressions.
Node.nodeType.
string.replace().
String.substring().
typeof variable.
Short questioion, I'm trying to understand this tutorial:
http://superdit.com/2011/02/09/jquery-memory-game/
Being new to Javascript I can't seem to find what the statement '== ""' means... I understand "==", but not the empty double quotes.
val == "" is a non-strict comparison to emtpy string. It will evaluate to true if val is empty, 0, false or [] (empty array):
var val = "";
console.log( val == "" ); // true
val = 0;
console.log( val == "" ); // true
val = false;
console.log( val == "" ); // true
val = [];
console.log( val == "" ); // true
You can use === to use strict comparison, fex:
val = 0;
console.log( val === "" ); // false
The ' == "" ' is a check for an empty string. It will be true when the string is empty, and false whenever there are some characters inside it.
A quick scan of the code (ctrl-F is your friend) quickly teaches you that the only time such a statement occurs in the code is here: if (imgopened == ""), another search taught me that imgopened is an evil (global) variable that is initialized to "" at the very top of the script, and every time some action/function is done with whatever value it was assigned.
I suspect it's a sort of card game, where two identical imgs need to be clicked, in which case this var will reference the image currently turned. If it's empty, then all imgs are facing down, and this var is empty: "".In other words:
if (imgopened == "")//=== if no card is turned
{
//do X, most likely: turn card
}
else
{
//do Y
}
This could've been written as
if (!imgopened)
//or
if (imgopened == false)//falsy, but somewhat confusing
//or
if (imgopened == 0)//!confusing, don't use
//or, my personal favorite
if (imgopened === '')
Using plain JavaScript (not jQuery), Is there any way to check if an element contains a class?
Currently, I'm doing this:
var test = document.getElementById("test");
var testClass = test.className;
switch (testClass) {
case "class1":
test.innerHTML = "I have class1";
break;
case "class2":
test.innerHTML = "I have class2";
break;
case "class3":
test.innerHTML = "I have class3";
break;
case "class4":
test.innerHTML = "I have class4";
break;
default:
test.innerHTML = "";
}
<div id="test" class="class1"></div>
The issue is that if I change the HTML to this...
<div id="test" class="class1 class5"></div>
...there's no longer an exact match, so I get the default output of nothing (""). But I still want the output to be I have class1 because the <div> still contains the .class1 class.
Use element.classList .contains method:
element.classList.contains(class);
This works on all current browsers and there are polyfills to support older browsers too.
Alternatively, if you work with older browsers and don't want to use polyfills to fix them, using indexOf is correct, but you have to tweak it a little:
function hasClass(element, className) {
return (' ' + element.className + ' ').indexOf(' ' + className+ ' ') > -1;
}
Otherwise you will also get true if the class you are looking for is part of another class name.
DEMO
jQuery uses a similar (if not the same) method.
Applied to the example:
As this does not work together with the switch statement, you could achieve the same effect with this code:
var test = document.getElementById("test"),
classes = ['class1', 'class2', 'class3', 'class4'];
test.innerHTML = "";
for(var i = 0, j = classes.length; i < j; i++) {
if(hasClass(test, classes[i])) {
test.innerHTML = "I have " + classes[i];
break;
}
}
It's also less redundant ;)
The easy and effective solution is trying .contains method.
test.classList.contains(testClass);
In modern browsers, you can just use the contains method of Element.classList :
testElement.classList.contains(className)
Demo
var testElement = document.getElementById('test');
console.log({
'main' : testElement.classList.contains('main'),
'cont' : testElement.classList.contains('cont'),
'content' : testElement.classList.contains('content'),
'main-cont' : testElement.classList.contains('main-cont'),
'main-content' : testElement.classList.contains('main-content'),
'main main-content' : testElement.classList.contains('main main-content')
});
<div id="test" class="main main-content content"></div>
Supported browsers
(from CanIUse.com)
Polyfill
If you want to use Element.classList but you also want to support older browsers, consider using this polyfill by Eli Grey.
Element.matches()
element.matches(selectorString)
According to MDN Web Docs:
The Element.matches() method returns true if the element would be selected by the specified selector string; otherwise, returns false.
Therefore, you can use Element.matches() to determine if an element contains a class.
const element = document.querySelector('#example');
console.log(element.matches('.foo')); // true
<div id="example" class="foo bar"></div>
View Browser Compatibility
This question is pretty solidly answered by element.classList.contains(), but people got pretty extravagant with their answers and made some bold claims, so I ran a benchmark.
Remember that each test is doing 1000 iterations, so most of these are still very fast. Unless you rely extensively on this for a specific operation, you won't see a performance difference.
I ran some tests with basically every way to do this. On my machine, (Win 10, 24gb, i7-8700), classList.contains performed super well. So did className.split(' ') which is effectively the same.
The winner though is classList.contains(). If you're not checking for classList to be undefined, ~(' ' + v.className + ' ').indexOf(' ' + classToFind + ' ') creeps ahead 5-15%
Since he wants to use switch(), I'm surprised no one has put this forth yet:
var test = document.getElementById("test");
var testClasses = test.className.split(" ");
test.innerHTML = "";
for(var i=0; i<testClasses.length; i++) {
switch(testClasses[i]) {
case "class1": test.innerHTML += "I have class1<br/>"; break;
case "class2": test.innerHTML += "I have class2<br/>"; break;
case "class3": test.innerHTML += "I have class3<br/>"; break;
case "class4": test.innerHTML += "I have class4<br/>"; break;
default: test.innerHTML += "(unknown class:" + testClasses[i] + ")<br/>";
}
}
Here is a little snippet If you’re trying to check wether element contains a class, without using jQuery.
function hasClass(element, className) {
return element.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(element.className);
}
This accounts for the fact that element might contain multiple class names separated by space.
OR
You can also assign this function to element prototype.
Element.prototype.hasClass = function(className) {
return this.className && new RegExp("(^|\\s)" + className + "(\\s|$)").test(this.className);
};
And trigger it like this (very similar to jQuery’s .hasClass() function):
document.getElementById('MyDiv').hasClass('active');
className is just a string so you can use the regular indexOf function to see if the list of classes contains another string.
This is a little old, but maybe someone will find my solution helpfull:
// Fix IE's indexOf Array
if (!Array.prototype.indexOf) {
Array.prototype.indexOf = function (searchElement) {
if (this == null) throw new TypeError();
var t = Object(this);
var len = t.length >>> 0;
if (len === 0) return -1;
var n = 0;
if (arguments.length > 0) {
n = Number(arguments[1]);
if (n != n) n = 0;
else if (n != 0 && n != Infinity && n != -Infinity) n = (n > 0 || -1) * Math.floor(Math.abs(n));
}
if (n >= len) return -1;
var k = n >= 0 ? n : Math.max(len - Math.abs(n), 0);
for (; k < len; k++) if (k in t && t[k] === searchElement) return k;
return -1;
}
}
// add hasClass support
if (!Element.prototype.hasClass) {
Element.prototype.hasClass = function (classname) {
if (this == null) throw new TypeError();
return this.className.split(' ').indexOf(classname) === -1 ? false : true;
}
}
A simplified oneliner:1
function hasClassName(classname,id) {
return String ( ( document.getElementById(id)||{} ) .className )
.split(/\s/)
.indexOf(classname) >= 0;
}
1 indexOf for arrays is not supported by IE (ofcourse). There are plenty of monkey patches to be found on the net for that.
I know there a lot of answers but most of these are for additional functions and additional classes. This is the one I personally use; much cleaner and much less lines of code!
if( document.body.className.match('category-page') ) {
console.log('yes');
}
I've created a prototype method which uses classList, if possible, else resorts to indexOf:
Element.prototype.hasClass = Element.prototype.hasClass ||
function(classArr){
var hasClass = 0,
className = this.getAttribute('class');
if( this == null || !classArr || !className ) return false;
if( !(classArr instanceof Array) )
classArr = classArr.split(' ');
for( var i in classArr )
// this.classList.contains(classArr[i]) // for modern browsers
if( className.split(classArr[i]).length > 1 )
hasClass++;
return hasClass == classArr.length;
};
///////////////////////////////
// TESTS (see browser's console when inspecting the output)
var elm1 = document.querySelector('p');
var elm2 = document.querySelector('b');
var elm3 = elm1.firstChild; // textNode
var elm4 = document.querySelector('text'); // SVG text
console.log( elm1, ' has class "a": ', elm1.hasClass('a') );
console.log( elm1, ' has class "b": ', elm1.hasClass('b') );
console.log( elm1, ' has class "c": ', elm1.hasClass('c') );
console.log( elm1, ' has class "d": ', elm1.hasClass('d') );
console.log( elm1, ' has class "a c": ', elm1.hasClass('a c') );
console.log( elm1, ' has class "a d": ', elm1.hasClass('a d') );
console.log( elm1, ' has class "": ', elm1.hasClass('') );
console.log( elm2, ' has class "a": ', elm2.hasClass('a') );
// console.log( elm3, ' has class "a": ', elm3.hasClass('a') );
console.log( elm4, ' has class "a": ', elm4.hasClass('a') );
<p class='a b c'>This is a <b>test</b> string</p>
<svg xmlns="http://www.w3.org/2000/svg" width="100px" height="50px">
<text x="10" y="20" class='a'>SVG Text Example</text>
</svg>
Test page
Here's a case-insensitive trivial solution:
function hasClass(element, classNameToTestFor) {
var classNames = element.className.split(' ');
for (var i = 0; i < classNames.length; i++) {
if (classNames[i].toLowerCase() == classNameToTestFor.toLowerCase()) {
return true;
}
}
return false;
}
Felix's trick of adding spaces to flank the className and the string you're searching for is the right approach to determining whether the elements has the class or not.
To have different behaviour according to the class, you may use function references, or functions, within a map:
function fn1(element){ /* code for element with class1 */ }
function fn2(element){ /* code for element with class2 */ }
function fn2(element){ /* code for element with class3 */ }
var fns={'class1': fn1, 'class2': fn2, 'class3': fn3};
for(var i in fns) {
if(hasClass(test, i)) {
fns[i](test);
}
}
for(var i in fns) iterates through the keys within the fns map.
Having no break after fnsi allows the code to be executed whenever there is a match - so that if the element has, f.i., class1 and class2, both fn1 and fn2 will be executed.
The advantage of this approach is that the code to execute for each class is arbitrary, like the one in the switch statement; in your example all the cases performed a similar operation, but tomorrow you may need to do different things for each.
You may simulate the default case by having a status variable telling whether a match was found in the loop or not.
If the element only has one class name you can quickly check it by getting the class attribute. The other answers are much more robust but this certainly has it's use cases.
if ( element.getAttribute('class') === 'classname' ) {
}
See this Codepen link for faster and easy way of checking an element if it has a specific class using vanilla JavaScript~!
hasClass (Vanilla JS)
function hasClass(element, cls) {
return (' ' + element.className + ' ').indexOf(' ' + cls + ' ') > -1;
}
This is supported on IE8+.
First we check if classList exists if it does we can use the contains method which is supported by IE10+. If we are on IE9 or 8 it falls back to using a regex, which is not as efficient but is a concise polyfill.
if (el.classList) {
el.classList.contains(className);
} else {
new RegExp('(^| )' + className + '( |$)', 'gi').test(el.className);
}
Alternatively if you are compiling with babel you can simply use:
el.classList.contains(className);
To check if an element contains a class, you use the contains() method of the classList property of the element:*
element.classList.contains(className);
*Suppose you have the following element:
<div class="secondary info">Item</div>*
To check if the element contains the secondary class, you use the following code:
const div = document.querySelector('div');
div.classList.contains('secondary'); // true
The following returns false because the element doesn’t have the class error:
const div = document.querySelector('div');
div.classList.contains('error'); // false
I think that perfect solution will be this
if ($(this).hasClass("your_Class"))
alert("positive");
else
alert("Negative");
I would Poly fill the classList functionality and use the new syntax. This way newer browser will use the new implementation (which is much faster) and only old browsers will take the performance hit from the code.
https://github.com/remy/polyfills/blob/master/classList.js
This is a bit off, but if you have an event that triggers switch, you can do without classes:
<div id="classOne1"></div>
<div id="classOne2"></div>
<div id="classTwo3"></div>
You can do
$('body').click( function() {
switch ( this.id.replace(/[0-9]/g, '') ) {
case 'classOne': this.innerHTML = "I have classOne"; break;
case 'classTwo': this.innerHTML = "I have classTwo"; break;
default: this.innerHTML = "";
}
});
.replace(/[0-9]/g, '') removes digits from id.
It is a bit hacky, but works for long switches without extra functions or loops
As the accepted answer suggests, Element.className returns a string, so you can easily check if a class exists by using the indexOf() method:
element.className.indexOf('animated') > -1
If you are interested in the performance difference between indexOf vs classList.contains, using indexOf seems to be slightly faster. I did a quick benchmark performance test to check that. Here are my findings: ClassName.indexOf vs ClassList.contains.
Try this one:
document.getElementsByClassName = function(cl) {
var retnode = [];
var myclass = new RegExp('\\b'+cl+'\\b');
var elem = this.getElementsByTagName('*');
for (var i = 0; i < elem.length; i++) {
var classes = elem[i].className;
if (myclass.test(classes)) retnode.push(elem[i]);
}
return retnode;
};
in which element is currently the class '.bar' ? Here is another solution but it's up to you.
var reg = /Image/g, // regexp for an image element
query = document.querySelector('.bar'); // returns [object HTMLImageElement]
query += this.toString(); // turns object into a string
if (query.match(reg)) { // checks if it matches
alert('the class .bar is attached to the following Element:\n' + query);
}
jsfiddle demo
Of course this is only a lookup for 1 simple element <img>(/Image/g) but you can put all in an array like <li> is /LI/g, <ul> = /UL/g etc.
Just to add to the answer for people trying to find class names within inline SVG elements.
Change the hasCLass() function to:
function hasClass(element, cls) {
return (' ' + element.getAttribute('class') + ' ').indexOf(' ' + cls + ' ') > -1;
}
Instead of using the className property you'll need to use the getAttribute() method to grab the class name.
I created these functions for my website, I use only vanilla javascript, maybe it will help someone.
First I created a function to get any HTML element:
//return an HTML element by ID, class or tag name
var getElement = function(selector) {
var elements = [];
if(selector[0] == '#') {
elements.push(document.getElementById(selector.substring(1, selector.length)));
} else if(selector[0] == '.') {
elements = document.getElementsByClassName(selector.substring(1, selector.length));
} else {
elements = document.getElementsByTagName(selector);
}
return elements;
}
Then the function that recieve the class to remove and the selector of the element:
var hasClass = function(selector, _class) {
var elements = getElement(selector);
var contains = false;
for (let index = 0; index < elements.length; index++) {
const curElement = elements[index];
if(curElement.classList.contains(_class)) {
contains = true;
break;
}
}
return contains;
}
Now you can use it like this:
hasClass('body', 'gray')
hasClass('#like', 'green')
hasClass('.button', 'active')
Hope it will help.
Tip: Try to remove dependencies of jQuery in your projects as much as you can - VanillaJS.
document.firstElementChild returns <html> tag then the classList attribute returns all classes added to it.
if(document.firstElementChild.classList.contains("your-class")){
// <html> has 'your-class'
} else {
// <html> doesn't have 'your-class'
}
Since .className is a string, you can use the string includes() method to check if your .className includes your class name:
element.className.includes("class1")
Using the classList is also ideal
HTML
<div id="box" class="myClass"></div>
JavaScript
const element = document.querySelector("#box");
element.classList.contains("myClass");
For me the most elegant and faster way to achieve it is:
function hasClass(el, cl) {
return el.classList ? el.classList.contains(cl) : !!el.className && !!el.className.match(new RegExp('(?: |^)' + cl + '(?: |$)'));
}
So, this happens to me quite frequently, but here's my latest one:
var generic_error = function(title,msg){
if(!title){ title= 'Oops!'; }
if(!msg) { msg = 'Something must have gone wrong, but no worries we\'re working on it!'; }
$.fancybox(
{
content:'\
<div class="error_alert">\
<h2>'+title+'</h2>\
<p>'+msg+'\
</div>'
});
}
Is there a cleaner way to check all params like title and msg above and OR set them as optional OR define defaults in the function like how PHP does it for example? Sometimes i could have 10 options and if(!var){var='defaults'} x 10 is icky...
Slightly shorter but equivalent to what you're doing now is to use "||" AKA "or" AKA "the default operator".
title = title || 'Oops!';
msg = msg || 'Something must have gone wrong, but no worries we\'re working on it!';
I doubt you'll find anything considerably shorter and simpler than if(!title)title='DefaultTitle' for function arguments.
However, I'd even use the longer form to make it more explicit: if (title===null) title='DefaultTitle'.
Here is a related question with an answer, but I think it would just makes your code more complicated. How can I access local scope dynamically in javascript?
You could use ternary notation as recommended by this article but in a simpler form:
var n = null;
!title ? title = 'Oops' : n;
You've also got the arguments[] array which holds the arguments and could be used in a loop, something like this:
function test(one,two,three) {
i=0;
while(typeof(arguments[i]) != 'undefined') {
alert(arguments[i++]);
}
}
test(40,27,399);
switch (arguments.length) {
case 0: title = 'Oops';
case 1: message = 'Something must have gone wrong...';
}
Here's another approach. The argsOK function is a little complex, but calling it is easy.
//-----------------------------------------------------
/*
PURPOSE Ensures a function received all required arguments, no extra
arguments & (if so specified) no arguments are empty.
RETURNS True if the arguments validate, else false.
*/
function argsOk(
functionCallee , // Caller's callee object
allArgsRequired , // True = All arguments are required
emptyArgsAllowed // True = Empty arguments are allowed
){
var ok = true;
for (var i = 0; i < 1; ++i) {
var functionName = functionCallee.toString().split(' ')[1].split('(')[0];
var args = functionCallee.arguments;
var expectedArgCount = functionCallee.length;
var actualArgCount = args.length;
if ((allArgsRequired && actualArgCount < expectedArgCount) ||
(actualArgCount > expectedArgCount)) {
error("Function " + functionName + " expected " + expectedArgCount + " arguments, but received " + actualArgCount + ".");
ok = false;
break;
}
if (emptyArgsAllowed) {
break;
}
for (var j = 0; j < args.length; ++j) {
if (args[j] != null && args[j].length == 0) {
error("Function " + functionName + "() received an empty argument.");
ok = false;
break;
}
}
}
return ok;
}
Example of calling it (a one-liner, as you can see):
//------------------------------------------------
function image(item, name, better)
// PURPOSE Write a request for picture or photo
// ENTRY Init() has been called
{
if (!showingShortVersion()) {
var betterString = '';
if (better != null && better == true)
betterString = 'better ';
if (argsOk(arguments.callee, true, false))
write('<p class="request maintain">If you have access to a ' + betterString + item + ' of ' + name + ' that we could put online, please click here.</p>');
}
}
In general, especially in Javascript, clean != short.
Do not use if(!title){ title= 'Oops!'; } as a general solution, because e.g. 0 and empty string are falsy, too. Arguments that are not set, are undefined, so I prefer using
if (title === undefined) {
title= 'Oops!';
}
It may be more wordy to do so, but It will prevent unwanted side effects, and in my experience, Javascript generates a lot of unwanted side effects, if you try to use shortcuts.