element.onclick返回null，element.getAttribute（'onclick'）不返回

Question

I thought that element.getAttribute('onclick') returns a string-version of whatever element.onclick is set to.

var as = document.getElementsByTagName('a');
for(var i=0; i < as.length; i++) {
    // set test to some javascript text
    var test = as[i].getAttribute('onclick');

     // set test to "null"
    var test = String(as[i].onclick);
}

Why is the ".onclick" notation returning null, when the .getAttribute('onclick') shows a value?

Answer 1

.onclick

returns the function that is bound to the click event.

.getAttribute('onclick')

returns the string value of the attribute.

In plain HTML, if the code of the attribute is invalid, there is no click event defined and the first will return null.

In any case, the two will not return the same thing. The first returns a function , the second a string .

Answer 2

By as[i].getAttribute('onclick') you are getting value of attribute named "onclick" in element dom. It is used to get any existing attribute and not specific to onclick

and function as[i].onclick is used to define event, not to get any value.

Basic use of onclick :

as[i].onclick=function() {

   console.log('print when clicked');

};