文档加载

window.addEventListener('load', function() {
    console.log('load')
})
window.addEventListener('pageshow', function(event) {
    console.log('pageshow')
})
window.addEventListener('unload', function() {
    console.log('unload')
})
window.addEventListener('pagehide', function(event) {
    console.log('pagehide')
})
document.addEventListener('DOMContentLoaded', function() {
    console.log('DOMContentLoaded')
})

document.addEventListener('readystatechange', function(e) {
    console.log(document.readyState)
})
  
/*    
if (document.readyState === 'complete') {
} else {
    document.addEventListener('DOMContentLoaded', function(e) {
    }, false);
}
*/

// addEventListener 无效
window.onbeforeunload = function() {
    return '确认退出？'
}