I have some typescript code, and I'm doing some metaprogramming where I need to be able to access instance.func.name
, however TypeScript omits the function name in the compiled JS.
TypeScript:
class ClassName {
// ...
func(): ReturnType {
// ...
}
}
Compiled JavaScript:
// ...
ClassName.prototype.func = function () {
// ...
};
Desired JavaScript:
ClassName.prototype.func = function func() {
// ... ^^^^
};
Is there a compiler option I'm missing, or a keyword I can use in TypeScript to accomplish this?
A solution, once which I will not be marking as accepted, because it doesn't provide the name
property, but does work with any other identifier is as follows:
function named(target: any, key: string) {
target[key].functionName = key;
}
class ClassName {
// ...
@named
func(): ReturnType {
// ...
}
}
Then access instance.func.functionName
.
It is not possible to use TypeScript decorators because function.name
is readonly property.
There is a hacky way:
class ClassName {
// ...
public func = function test() {
}
public func2() {
}
}
let instance = new ClassName();
console.log("RESULT", instance.func['name']);
but it is not exactly what you ask for (i.e. notice the missing prototype in the function declaration).
Edit: TypeScript compiler does not write the function name because there is no handling for SyntaxKind.MethodDeclaration
in emitter.ts:
function shouldEmitFunctionName(node: FunctionLikeDeclaration) {
if (node.kind === SyntaxKind.FunctionExpression) {
// Emit name if one is present
return !!node.name;
}
if (node.kind === SyntaxKind.FunctionDeclaration) {
// Emit name if one is present, or emit generated name in down-level case (for export default case)
return !!node.name || languageVersion < ScriptTarget.ES6;
}
}
If you want to get your hands dirty, then you can update ./node_modules/typescript/lib/typescript.js
file. Just add the last condition:
function shouldEmitFunctionName(node) {
if (node.kind === 173 /* FunctionExpression */) {
// Emit name if one is present
return !!node.name;
}
if (node.kind === 213 /* FunctionDeclaration */) {
// Emit name if one is present, or emit generated name in down-level case (for export default case)
return !!node.name || languageVersion < 2 /* ES6 */;
}
// MODIFIED
if (node.kind === 143 /* MethodDeclaration */) {
return true;
}
}
and run this to test the change:
$ node ./node_modules/typescript/lib/typescript.js hello.ts