Question

如果变量存在于不执行的if语句中，则变量会被初始化/存储在内存中，如下所示：

function blah(){
    if(something === true){
        var blahOne = 1;
        var blahTwo = 2;
        var blahThree = 3;
    } else {
        console.log('The above if statement usually won\'t execute');
    }
}

我的假设是否定的，但Javascript至少可以说是一种古怪的语言。在此先感谢您的帮助！

Answer 1

所有var声明都移到函数顶部并初始化为undefined。这称为可变吊装。 JavaScript没有块范围，只有函数和全局范围。

您的代码等同于以下

function blah(){
    var blahOne, blahTwo, blahTree;
    if(something === true){
        blahOne = 1;
        blahTwo = 2;
        blahThree = 3;
    } else {
        // blahOne, blahTwo, blahThree are set to undefined
        console.log('The above if statement usually won\'t execute');
        // But since they have been declared, there's no error in reading them
        console.log(blahOne, blahTwo, blahThree);
    }
}

Answer 2

Javascript中没有像block scope这样的东西。见article。如果你想这样说：Javascript有功能范围。所以问题的答案是yes它们被初始化了。

Javascript内存节省 - 如果语句var声明

2 个答案: