Analyze javascript file using Typescript Compiler

Question

Refer to: https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API, I want to get type of node in AST.

It is successful for angular project because it is written using typescript and tsconfig.json exists.

When I try to analyze react app which is written using javascript

const program = ts.createProgram({
    rootNames: [fileName],
    options: {
        strict: true,
        target: ts.ScriptTarget.ES2015,
        allowJs: true,
        checkJs: true
    }
})
const typeChecker = program.getTypeChecker();
... ...

I get: typechecker.getTypeAtLocation(node).getSymbol() is undefined.

I assume options of ts.createProgram is wrong.

I think typeChecker.getTypeAtLocation(node) might be returning the error type. Are there any diagnostics returned by ts.getPreEmitDiagnostics(program)? — David Sherret
– David Sherret, Commented May 14, 2019 at 19:46

Tody.Lu · Accepted Answer · 2019-05-16 06:04:28Z

1

the option: moduleResolution: ts.ModuleResolutionKind.NodeJs is key.

const program = ts.createProgram({
    rootNames: [file1],
    options: {
        strict: true,
        target: ts.ScriptTarget.ES2015,
        allowJs: true,
        checkJs: true,
        moduleResolution: ts.ModuleResolutionKind.NodeJs
    }
})

The above works for React JS.

answered May 16, 2019 at 6:04

Tody.Lu

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1 Comment

David Sherret Over a year ago

For some background, this solution depends on the scenario and the reason this occurs is because when targeting ES2015 or above, the default module resolution will change from NodeJs to Classic. So this isn't because a JS file was being analyzed and what you were probably getting was the unknown type. Read more in my answer here.

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