How to use js to judge whether dom has a value of class
- 2021-07-21 05:40:22
- OfStack
For example:
<html class="no-js">
<head>
</head>
<body>
</body>
</html>
It is judged whether the class of the html node has no-js.
1. Implementation of jquery
$("html").hasClass('no-js');
jquery source code implementation:
var rclass = /[\t\r\n\f]/g;
jQuery.fn.extend({
hasClass: function(selector) {
var className = " " + selector + " ",
i = 0,
l = this.length;
for (; i < l; i++) {
if (this[i].nodeType === 1 &&
(" " + this[i].className + " ").replace(rclass, " ").indexOf(className) > -1) {
return true;
}
}
return false;
}
})
2. Implementation of js
function hasClass(element, cls) {
return (' ' + element.className + ' ').indexOf(' ' + cls + ' ') > -1;
}
hasClass(document.querySelector("html"), 'no-js');
3. classList for H5
Under the description:
The indexOf method of a string is indistinguishable from classes like. no-js and. no-js-indeed; The separator of the class name may not be a space, or it may be\ t, etc.Code:
var hasClass = (function(){
var div = document.createElement("div") ;
if( "classList" in div && typeof div.classList.contains === "function" ) {
return function(elem, className){
return elem.classList.contains(className) ;
} ;
} else {
return function(elem, className){
var classes = elem.className.split(/\s+/) ;
for(var i= 0 ; i < classes.length ; i ++) {
if( classes[i] === className ) {
return true ;
}
}
return false ;
} ;
}
})() ;
alert( hasClass(document.documentElement, "no-js") ) ;