onclick event fires before button clicked - javascript

问题

I have a pop up window with a button. When I click the button I want something to happen, say an alert.

The issue I am having is that the onclick event fires as soon as the popup is launched and not when the button is clicked.

Here is the code. Any thoughts will be much appreciated.

var popup = open("", "Popup", "width=300,height=200");
var btn = popup.document.createElement("button");
btn.style.height = "50px";
btn.style.width = "150px";
popup.document.body.appendChild(btn);

btn.innerHTML="button1";
btn.onclick = alert("hello");

回答1:

In your code

btn.onclick = alert("hello");

onclick is not fired. Just alert is executed immediately. You should wrap it into a function:

btn.onclick = function(){ alert("hello");}

回答2:

assign function to the btn.onclick event.

来源：https://stackoverflow.com/questions/17351853/onclick-event-fires-before-button-clicked-javascript