Javascript 生成冗余变量的类型脚本
考虑以下类型脚本代码:Javascript 生成冗余变量的类型脚本,javascript,compilation,typescript,Javascript,Compilation,Typescript,考虑以下类型脚本代码: module demoAppModule{ 'use strict'; export module nest{ export var hello = function () { alert('Hello!'); }; } } demoAppModule.nest.hello(); var demoAppModule; (function (demoAppModule) { 'us
module demoAppModule{
'use strict';
export module nest{
export var hello = function () {
alert('Hello!');
};
}
}
demoAppModule.nest.hello();
var demoAppModule;
(function (demoAppModule) {
'use strict';
(function (nest) {
nest.hello = function () {
alert('Hello!');
};
})(demoAppModule.nest || (demoAppModule.nest = {}));
var nest = demoAppModule.nest;
})(demoAppModule || (demoAppModule = {}));
demoAppModule.nest.hello();
传输后,我们有以下javascript代码:
module demoAppModule{
'use strict';
export module nest{
export var hello = function () {
alert('Hello!');
};
}
}
demoAppModule.nest.hello();
var demoAppModule;
(function (demoAppModule) {
'use strict';
(function (nest) {
nest.hello = function () {
alert('Hello!');
};
})(demoAppModule.nest || (demoAppModule.nest = {}));
var nest = demoAppModule.nest;
})(demoAppModule || (demoAppModule = {}));
demoAppModule.nest.hello();
为什么会生成此行?我的眼睛疼
var nest = demoAppModule.nest;
简短回答:需要在本地访问模块变量。例如
module demoAppModule{
'use strict';
export module nest{
export var hello = function () {
alert('Hello!');
};
}
// The following would not be possible without that line
console.log(nest.hello);
}
demoAppModule.nest.hello();
更详细的回答:它类似于模块前添加的var,例如注意var x
:
// TypeScript
module x{export var foo;}
// Generated JavaScript
var x;
(function (x) {
x.foo;
})(x || (x = {}));
但是,当您在模块内+导出模块时,var
需要添加到outermoule.innermodule
中,因此您不需要预先执行var innermodule
。将其添加到outermodule
,然后创建一个局部变量以指向innermodule
,您可以在生成的javascript中看到该变量:
// Notice var here
var demoAppModule;
(function (demoAppModule) {
'use strict';
// Notice no var here
(function (nest) {
nest.hello = function () {
alert('Hello!');
};
})(demoAppModule.nest || (demoAppModule.nest = {}));
// Notice var assinged afterwards
var nest = demoAppModule.nest;
// The following would not be possible without that line
console.log(nest.hello);
})(demoAppModule || (demoAppModule = {}));
demoAppModule.nest.hello();
那句话对我来说似乎毫无用处。我能想到的唯一原因是编译器认为必须在函数
hello
之前定义参数nest
,但是赋值发生在最底层,然后对它不做任何处理。谢谢。读了这篇文章,我意识到如果我后来使用了nest,就像您的示例中的日志记录一样,它看起来就不会那么不必要了。