如何使用JavaScript将onclick事件添加到元素

Question

I have created an element using document.getElementsByClassname, and would like to add a onclick event to this element, so that when someone clicks on this element onclick function should be called.

I tried with event listener, but this will execute even when I don't click on any function. Using jQuery we can do that by binding a click event, but I my requirement is in javascript/

Thanks!

element.addEventListener("click", alert('clicked'), false);// Add onclick eventListener 

var element= document.getElementsByClassName('classname');

Answer 1

getElementsByClassName returns an HTMLCollection , so even though you have only one element with that classname in DOM, you have to retrieve it with index 0:

var element = document.getElementsByClassName('classname')[0];
element.addEventListener("click", function(e) {
    alert('something');
}, false);

Alternatively, since you only have one element with the classname, you can safely use querySelector , which will return the first match element.

var element = document.querySelector('.classname');
                                      ^
element.addEventListener("click", function(e) {
    alert('something');
}, false);

Please note the dot in above code. querySelector accepts a CSS selector string as a parameter.

Answer 2

Try this:
document.getElementsByClassName always returns array of elements.

 var element= document.getElementsByClassName('classname');
 for(var i=0;i<element.length;i++){
      element[i].addEventListener("click", function(){alert('clicked')}, false);   
 }

Answer 3

You have to pass reference of a function instead of adding inline alert.

var element= document.getElementsByClassName('classname');
function doSomething() {
  alert('clicked')
}

// add event listener to element 
element.addEventListener("click", doSomething, false);

Answer 4

You can use .attr() jquery method for this:

$('.classname').attr("onClick", "javascript:alert('clicked'); return false;"); 

Try this

JavaScript

var element= document.getElementsByClassName('classname');
element[0].onclick = function() { alert('Hello'); };//-- here i used "[0]" to refer first matched element 

Try with javascript

Answer 5

You can use an event delegation or DOMNode.matches.

document.addEventListener('click', function(e) {
   if (e.target.className == 'classname') // if (e.target.matches('.classname'))
   {
       //do something
   }
});

Answer 6

Please try the following:

var rows = 3;
var cols = 3;
var defaultVal=0;
var mainDiv=document.getElementById("mainDiv")
var arr = []
for (var i = 0; i < rows; i++) {
    arr[i] = [];
  for(var j=0;j<cols;j++){
    arr[i][j]=defaultVal++;
    var element=document.createElement("input");
    element.type="button";
    element.className="left";
    element.addEventListener("click", testFunction, false);
    element.value=arr[i][j];
    mainDiv.appendChild(element);


  }


}
function testFunction(){
    alert('hi')
}

//Use element.addEventListener("click", testFunction, false); 
//Use testFunction and not testFunction() as this "()" invokes the function

Answer 7

I was able to add an onclick event to an element using following javascript code

list_title = document.createElement('UL');
list_title.onclick=function() {

    // place your code here
};