Variables JScript.NET专用变量
我想知道JScript.NET私有变量。请查看以下代码:Variables JScript.NET专用变量,variables,closures,private,jscript.net,Variables,Closures,Private,Jscript.net,我想知道JScript.NET私有变量。请查看以下代码: import System; import System.Windows.Forms; import System.Drawing; var jsPDF = function(){ var state = 0; var beginPage = function(){ state = 2; out('beginPage'); } var out = function(text){ if(state == 2){
import System;
import System.Windows.Forms;
import System.Drawing;
var jsPDF = function(){
var state = 0;
var beginPage = function(){
state = 2;
out('beginPage');
}
var out = function(text){
if(state == 2){
var st = 3;
}
MessageBox.Show(text + ' ' + state);
}
var addHeader = function(){
out('header');
}
return {
endDocument: function(){
state = 1;
addHeader();
out('endDocument');
},
beginDocument: function(){
beginPage();
}
}
}
var j = new jsPDF();
j.beginDocument();
j.endDocument();
输出:
beginPage 2
header 2
endDocument 2
如果在任何浏览器中运行相同的脚本,则输出为:
beginPage 2
header 1
endDocument 1
为什么会这样
谢谢,
Paul.只是猜测,但是JScript.NET似乎不像EMCAScript那样支持闭包,因此endDocument()中的
state
变量不是引用外部函数的私有成员,而是一个局部变量(未声明)。奇怪。在这里调用jsPDF时不必使用new,因为您使用的是单例模式。jsPDF将返回一个对象文本,因此即使没有新文本,您也可以访问beginPage和endDocument方法。老实说,我不知道在返回对象文字的函数上使用new时,规范会调用什么,所以我不确定JScript.NET是错误的还是浏览器错误的。但现在,请尝试删除新的before jsPDF(),或者将函数更改为:
var jsPDF = function(){
var state = 0;
var beginPage = function(){
state = 2;
out('beginPage');
};
var out = function(text){
if(state == 2){
var st = 3;
}
MessageBox.Show(text + ' ' + state);
};
var addHeader = function(){
out('header');
};
this.endDocument = function(){
state = 1;
addHeader();
out('endDocument');
};
this.beginDocument: function(){
beginPage();
};
}
这将允许您使用new关键字并创建多个jsPDF对象。我遇到了同样的问题。在下面的代码中,绑定到fun的闭包应该只包含一个名为result的变量。正如代码所示,带有一个参数的函数中的变量result似乎与闭包中的结果变量不同
var fun = function() {
var result = [];
// recursive descent, collects property names of obj
// dummy parameter does nothing
var funAux = function(obj, pathToObj, dummy) {
if (typeof obj === "object") {
for (var propName in obj) {
if (obj.hasOwnProperty(propName)) {
funAux(obj[propName], pathToObj.concat(propName), dummy);
}
}
}
else {
// at leaf property, save path to leaf
result.push(pathToObj);
}
}
return function(obj) {
// remove line below and `result' 3 lines below is `result' in closure
result = []; // does not appear to be bound to `result' above
funAux(obj, [], "dummy");
return result; // if result 2 lines above is set, result is closure is a different variable
};
}();
如果在这个函数中
result = [];
删除,然后在行中显示结果
return result;
指闭包中的结果
var fun = function() {
var result = [];
// recursive descent, collects property names of obj
// dummy parameter does nothing
var funAux = function(obj, pathToObj, dummy) {
if (typeof obj === "object") {
for (var propName in obj) {
if (obj.hasOwnProperty(propName)) {
funAux(obj[propName], pathToObj.concat(propName), dummy);
}
}
}
else {
// at leaf property, save path to leaf
result.push(pathToObj);
}
}
return function(obj) {
// remove line below and `result' 3 lines below is `result' in closure
result = []; // does not appear to be bound to `result' above
funAux(obj, [], "dummy");
return result; // if result 2 lines above is set, result is closure is a different variable
};
}();
不,他们认为他们支持关闭-