Typescript 和 Uncaught SyntaxError：在严格模式之外尚不支持块范围的声明（let、const、function、class）
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Typescript and Uncaught SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
提问by o..o
I have a typescript file containing a class definition:
我有一个包含类定义的打字稿文件：
if (window.console == null) {
(<any>window).console = {
error: function (a) {
},
log: function (a) {
}
};
}
class SendMessage {
//.....
}
After the compilation to javascript (by VS2015), I get the error on the line with the class definition:
编译为 javascript（通过 VS2015）后，我在类定义行上收到错误：
Uncaught SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
I have found that I have to use the strict mode. But why and how can I use it in typescript?
我发现我必须使用严格模式。但是为什么以及如何在打字稿中使用它？
Thanks
谢谢
回答by David Sherret
It's because it's compiling to ES6 and the browser is requiring that block-scoped declarations be used in strict mode.
这是因为它正在编译为 ES6，并且浏览器要求在严格模式下使用块范围的声明。
You can fix this by using strict mode. To do that add...
您可以使用严格模式解决此问题。要做到这一点，请添加...
"use strict";
...to the top of every file.
...到每个文件的顶部。
However, I think you probably want to change the compilation target from ES6 to ES5. If you are using tsconfig.json, change "target": "es6"to "target": "es5". Doing that will...compile to ES5...and so block-scoped declarations will be changed appropriately so "use strict";will not be required. Additionally, more browsers will support your code. Right now runtime ES6 support is still not widespread.
但是，我认为您可能希望将编译目标从 ES6 更改为 ES5。如果您正在使用tsconfig.json，请更改"target": "es6"为"target": "es5"。这样做将...编译为 ES5...因此块范围的声明将被适当更改，因此"use strict";不需要。此外，更多浏览器将支持您的代码。现在运行时 ES6 支持仍然不普遍。
Note that if you are not using tsconfig.json, you might have to change the target in the project properties' typescript build tab as shown here:
请注意，如果您不使用 tsconfig.json，则可能需要更改项目属性的 typescript 构建选项卡中的目标，如下所示：
