tsc-watch 抛出错误：“文件 'dist/index.js' 是 JavaScript 文件。 您的意思是启用“allowJs”选项吗？”

Question

I have a simple index.ts file I complied with tsc:

function printMessage(msg: string): void {
    console.log(`Message: ${msg}`);
}

printMessage("Hello, TypeScript");

When I run the command:

npx tsc-watch --onsuccess "node dist/index.js"

I get the error "File 'dist/index.js' is a JavaScript file. Did you mean to enable the 'allowJs option?" I've tried it with the allowJs option to true but it still generates the same error.

TypeScript version 3.9.7 tsc-watch version 4.2.9

Answer 1

I worked around this by installing tsc-watch globally:

npm intall -g tsc-watch

Then I could run the command without npx:

tsc-watch --onSuccess "node dist/index.js"

Which worked fine now. Looking at your code it seems you are also following the Essential TypeScript book Chapter 5 page 114 in case others will search for these terms.

Still don't understand why the original command doesn't work. As Aluan mentioned in his comment it seems that the index.js file is actually passed to tsc-watch as it complains that it wants to compile a.js file instead of.ts files.

Answer 2

This problem is caused by the way that PowerShell parses arguments. Here is the escape sequence that will solve the problem:

npx tsc-watch --onSuccess "\`"node dist\index.js\`""

Those are double quotes and back ticks. The result is that PowerShell passes on the "node dist/index.js" argument without parsing it.