{JS} function statement

The output result of the following statement is as follows:
Alert (f (4 ));
Var f = 0;
Function f (x ){
Return x + 1;
}
Alert (f );

The answer is:
// 5
// 0

Here we need to explain the cause-the reason for this result is that the function definition and variable definition occur at different times.
Function definitions in JS occur during parsing, rather than during runtime. when the JS parser encounters a function definition, it will parse and store (without executing) The statements that constitute the function body, define an attribute with the same name as the function. (If the function definition is nested in other functions, this attribute will be defined in the calling object; otherwise, this attribute will be defined in the Global Object) to save it.

As mentioned above, you can understand why the function definition in JS cannot appear in if/while or other statements, as shown below:
If (a = 1 ){
Function get (param ){
Return param + 1;
}
} Else {
Function get (param ){
Return param + 2; www.2cto.com
}
}

Because the function definition occurs during parsing, The get function is always the second one.

By bill200711022