JavaScript事件处理程序执行顺序 [英] JavaScript event handlers execution order
问题描述
document.getElementById('e1')。addEventListener('click',function() {alert('1');},false);
document.getElementById('e2')。addEventListener('click',function(){alert('2');},false);
document.getElementById('e1')。click();
document.getElementById('e2')。click();
我想知道警报显示的顺序如何 - 事件顺序是由 click()
触发的,还是可以是随机的?
标准化的行为,而不是目前实现的浏览器。
警报将按顺序执行 - 1
然后 2
。这是因为单击
事件是同步的(请参阅这里) - 当 .click()
被发出时,处理程序将立即运行(看最后一段< a href =http://www.w3.org/TR/DOM-Level-3-Events/#event-flow =nofollow> here )。所以这个代码:
document.getElementById('e1')。addEventListener('click',function(){alert 1');},false);
document.getElementById('e2')。addEventListener('click',function(){alert('2');},false);
document.getElementById('e1')。click();
document.getElementById('e2')。click();
alert('3');
将产生与
<$ p相同的结果$ p>
警报( '1');
alert('2');
alert('3');
Having this JS code:
document.getElementById('e1').addEventListener('click', function(){alert('1');}, false);
document.getElementById('e2').addEventListener('click', function(){alert('2');}, false);
document.getElementById('e1').click();
document.getElementById('e2').click();
I'm wondering in what order will the alerts show up - will it be in the order the events were triggered by click()
or could it be random?
I'm asking about documented/standardised behaviour, not about what browsers currently implement.
The alerts will be executed in order - 1
and then 2
. This is because click
event is synchronous (see here) - when .click()
is issued the handler will be run immediately (look at the last paragraph here). So this code:
document.getElementById('e1').addEventListener('click', function(){alert('1');}, false);
document.getElementById('e2').addEventListener('click', function(){alert('2');}, false);
document.getElementById('e1').click();
document.getElementById('e2').click();
alert('3');
will produce the same result as
alert('1');
alert('2');
alert('3');
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