${descriptor.resource.toString()}${descriptor.etag}

Isn't this better ? Es6 String Literals

@amarpathak what are you smoking?

@amadare42 That’s right. I think we can add a symbol between these two string to separate them.

${descriptor.resource.toString()}:${descriptor.etag}

@hwhung0111 well, I think you linked wrong person, but I want to mention that es6 string templating will call toString automatically so your line can be shortened:
${descriptor.resource}:${descriptor.etag}

This is is not the best solution. ES6 literals are not suited for this purpose but injecting dynamic data into strings.

@amadare42 I am sorry about that. And thanks for telling me about es6 string.
@KristofferTolboll2 If I add a colon in the string, is it better to use ES6 literals.

@hwhung0111 ES6 template literals are most used, when there are more static content, in this case, there is only the : which is static, everything else is dynamic, therefore it will decrease readability

@KristofferTolboll2 I get your point. But why I still found ${message}: [${err.toString()} and ${this.scope}.${key} in source code? These are similar to this issue.