Question

我在理解下面的全局变量x的生命周期时遇到了一些麻烦。我已经在线上评论了我不理解的问题..请帮助...谢谢

var target = document.getElementById("outputArea");
var outString = "";

var x = 0;
var y = 0;

callMeOften2();
callMeOften2();
callMeOften2();
outString += "<br/>";

target.innerHTML = outString;

function callMeOften2() {
    outString += x + "<br/>"; //why isn't this going to give an output of 0? but gave an output of undefined instead? isn't x referring to the global variable x?
    var x = 100;

    x = x + 100;
    outString += "from callMeoften2: " + "x = " + x + "<br/>";
}

Answer 1

以下是通过变量提升的所有Javascript引擎如何与您的代码一起播放（有效）

function callMeOften2() {
    var x = undefined;
    outString += x + "<br/>"; //why isn't this going to give an output of 0? but gave an output of undefined instead? isn't x referring to the global variable x?
    x = 100;

    x = x + 100;
    outString += "from callMeoften2: " + "x = " + x + "<br/>";
}

希望这有帮助

函数中的var x表示全局x无关紧要（当然可以在浏览器中使用window.x访问，其他一些＆＃34; global＆＃34;对象在其他环境中）

变量的时间

1 个答案: