diefference between 'function func(){}' and 'var func = function(){}' in javascript

javascript function的二种定义方式的区别

console.log(f); // undefined
console.log(h()); // true

// This line of code defines an unnamed function and stores a reference to it
// in the variable f. It does not store a reference to the function into a variable
// named fact, but it does allow the body of the function to refer to itself using
// that name.
var f = function fact(x) {
    if (x <= 1) return 1;
    else return x * fact(x - 1);
};
try {
    console.log(f);
    console.log(fact);
} catch (e) {
    console.error(e.message)
}
console.log(f(1));
console.log(f(2));
console.log(f(3));
var g = function(x) {
    if (x <= 1) {
        return 1;
    } else {
        return x * arguments.callee(x - 1);
    }
};
console.log(g(4));

function h() {
    return true;
}

其中需要说明一下var func = function(){}与function func(){}这二者的区别是后者用function语句定义的variable会先于此function运行前被初始化，因此h()函数调用可以写在其定义语句之前，而前者用var声明的variable则只能在此变量声明之后才可以被调用，与其他用var声明的变量完全一样。

另var f = function fact(x) { if (x <= 1) return 1; else return x * fact(x - 1); };这个写法要注意是在javascript 1.5版本之后才被实现。