javascript函数声明提前的一个例子

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#javascript函数声明提前的一个例 #javascript #function

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本文深入探讨了JavaScript中函数声明与赋值表达式的区别，解释了函数声明的提升机制，并通过示例展示了如何正确理解和使用它们。重点区分了函数名的提升与函数体的延迟执行，提供了清晰的代码示例帮助读者理解。

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Notice that the assignment portion of the declarations were not hoisted.Only the name is hoisted. This is not the case with function declarations,where the entire function body will be hoisted as well. But remember that thereare two normal ways to declare functions. Consider the following JavaScript:

function test() {

foo(); //TypeError "foo is not a function"

bar(); //"this will run!"

var foo =function () { // function expression assigned to local variable 'foo'

alert("thiswon't run!");

}

functionbar() { // function declaration, given the name 'bar'

alert("thiswill run!");

}

test();

In this case, only the function declaration has its body hoisted to thetop. The name ‘foo’ is hoisted, but the body is left behind, to be assignedduring execution.

That covers the basics of hoisting, which is not as complex or confusingas it seems. Of course, this being JavaScript, there is a little morecomplexity in certain special cases.