Javascript 以下几行代码有什么区别

Question

What is the difference between the following lines of codes, When we are using jquery. Is there anyone of them more preferable?

<script>
alert("hello");  // 1. alert hello 
$(function(){alert("hello");}); // 2. Also alert hello
(function($){alert("hello");})(jQuery); // 3. It also alert hello
</script>

Answer 1

• In the first line, you are just calling alert() .

• In the second line, you are trying to get a collection of matched elements either found in the DOM based on passed argument(s) or created by passing an HTML string ( more here ). So the parameter is evaluated and alert() is called.

• In the third line, you are calling a self invoking function and passing jQuery as parameter but not using it. and alert() is called.

TO SUM UP

The first line alert("hello"); is definitely the best, as the last two lines are causing useless computations just to alert.