变量未定义 - javascript

Question

我正在编写一个 AI。它不工作。浏览器显示：Uncaught ReferenceError: do is not defined.

var what = ["jokes", "cats", "news", "weather", "sport"];

function start() {

    var do = what[Math.floor((Math.random() * what.length) + 1)];
}
start();
Document.write(do);

Answer 1

var what = ["jokes", "cats", "news", "weather", "sport"];
var do;
function start() {

    do = what[Math.floor((Math.random() * what.length) + 1)];
}
start();
Document.write(do);

Answer 2

do 在这里是变量而不是函数。

var do = what[Math.floor((Math.random() * what.length) + 1)];

要创建一个 do 函数，您可以这样做。

var what = ["jokes", "cats", "news", "weather", "sport"];
var do;
function start() {    
    do = function(){ return what[Math.floor((Math.random() * what.length) + 1)]};
}
start();
Document.write(do());

Answer 3

Do 仅存在于您的函数中。阅读有关功能范围的信息:)试试这个：

var what = ["jokes", "cats", "news", "weather", "sport"];
var do = undefined;
function start() {
    do = what[Math.floor((Math.random() * what.length) + 1)];
}
start();
Document.write(do);

Answer 4

你做的变量超出范围

var what = ["jokes", "cats", "news", "weather", "sport"];

function start() {

    var do = what[Math.floor((Math.random() * what.length) + 1)];
}
start();
Document.write(do);

您需要将密码更改为

var what = ["jokes", "cats", "news", "weather", "sport"];

function start(callback) {

    var do = what[Math.floor((Math.random() * what.length) + 1)];
    callback(do);
}
start(function(val) {document.write(val)});

变量未定义 - javascript

Variable not defined - javascript

javascript

var

function