The differences between window.onload and document.ready

function t(){
	alert("test1")
}
function b(){
	alert("test2")
}
window.onload =t ;
window.onload =b ;

• window.onload fires later (or at the same time in the worst/failing cases) when images and such are loaded, so if you're using image dimensions for example, you often want to use this instead.
• 必须等到网页中所有内容加载完成后才能执行（包括图片）
• 不能同时编写多个
• 上述代码执行页面弹出“test2”

$(document).ready(function(){
	alert("Hello World!");
});


$(document).ready(function(){
	alert("Hello again!");
});

• document.ready is a jQuery event, it runs when the DOM is ready, e.g. all elements are there to be found/used, but not necessarily all content.
• 网页中Dom元素加载完成即可执行，也许与Dom元素相关联的并未加载完成
• 可以同时编写多个
• 上述代码执行页面先后弹出“Hello World!”、"Hello again!"