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There are three ways to define a function:
1. Keyword method
function Fnmethodname (x) { alert (x);}2. Literal method
var function (x) { alert (x);}3.Function () constructor
var New Function (' x ', ' Alert (x); ')The above three methods define the same method function Fnmethodname, the 1th is the most commonly used method, the latter two are to copy a function to the variable fnmethodname, and this function is no name, that is, anonymous function.
4. Defining anonymous Functions
<body onload= "alert (' http://www.baidu.com/');" > <script type= "Text/javascript" > voidfunction() { alert (' Pop-up box '); } (); </script> two notation <body onload= "alert (' http://www.baidu.com/');" > <script type= "Text/javascript" > (function() { alert ( ' popup box '); }) (); </script> A function with no function name, which extends the question of how to invoke an anonymous function.
Parentheses call
Why is this method successfully invoked?
The effect of parentheses:
Parentheses can combine our expressions and each block, that is, each pair of parentheses, has a return value. This return value is actually the return value of the expression in parentheses.
So, when we enclose the anonymous function with a pair of parentheses, the parentheses are actually returned, which is the function object of one of the anonymous functions.
Therefore, the parenthesis pair plus the anonymous function is like the name of the function that we get its reference position. So if you add a parameter list after the reference variable, the invocation form of the normal function is implemented.
JS function definition and anonymous function invocation
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