Using TypeScript with WebNN API

TypeScript (TS) provides strong typing capabilities for JavaScript projects, enhancing developer productivity with features like code completion and compile-time error checking. This guide explains how to integrate TypeScript type definitions for the WebNN API in your projects.

Overview

The @webnn/types package contains TypeScript declaration files (.d.ts) for the WebNN API, providing type information for methods, properties, and return values used in the WebNN specification.

Note: You don’t need to use @webnn/types if you’re working with JavaScript ML libraries like Transformers.js or ONNX Runtime Web , which may include their own type definitions.

Why Use Type Definitions?

Without type definitions, TypeScript will treat WebNN API objects and methods as having unknown type:

WebNN without TypeScript type definitions

Figure 1: Type unknown errors appear when no type definitions are available

With proper type definitions, TypeScript can provide code completion, parameter validation, and type checking:

Figure 2: Type checking works correctly when definitions are available

Installation

Install the type definitions as a development dependency using your preferred package manager:


# npm
npm install --save-dev @webnn/types
# yarn
yarn add --dev @webnn/types
# pnpm
pnpm add -D @webnn/types

Configuration

Since @webnn/types is outside of DefinitelyTyped (@types) , you need to explicitly configure TypeScript to recognize these types. You have two options:

Option 1: Using `types` in `tsconfig.json`

tsconfig.json


{
  "compilerOptions": {
    "types": ["@webnn/types"]
  }
}

Option 2: Using `typeRoots` in `tsconfig.json`

tsconfig.json


{
  "compilerOptions": {
    "typeRoots": [
      "./node_modules/@webnn/types",
      "./node_modules/@types"
    ]
  }
}

Figure 3: Configuration in tsconfig.json

Global Types

Once configured, the WebNN types are globally available in your project. You don’t need to import them explicitly - TypeScript will automatically recognize WebNN interfaces like navigator.ml and MLGraphBuilder.


// No need to import WebNN types - they're globally available
async function runInference() {
  // TypeScript will recognize these types
  const ml:ML = navigator.ml;
  const context:MLContext = navigator.ml.createContext();
  const builder:MLGraphBuilder = new MLGraphBuilder(context);
 
  const input:MLOperand = builder.input('input', {dataType: 'float32', shape: [1, 3, 224, 224]});
  const weights:MLOperand = builder.constant({dataType: 'float32', shape: [16, 3, 3, 3]}, new Float32Array(432));
 
  // Types for convolution parameters
  const options:MLConv2dOptions = {
    padding: [1, 1, 1, 1],
    strides: [1, 1],
    dilations: [1, 1],
    groups: 1
  };
  
  const conv:MLOperand = builder.conv2d(input, weights, options);
  const graph:MLGraph = await builder.build({output: conv});
  
  // Rest of the inference code...
}

TypeScript Vanilla Example

For a complete working example, refer to the WebNN TypeScript Vanilla Example repository, which demonstrates:

Tips for WebNN TS Development

Use TypeScript’s autocompletion to discover available methods and properties
Leverage parameter type checking to avoid common WebNN API usage errors
TypeScript interfaces will help you conform to the expected shapes of WebNN options objects
VSCode and other modern editors will show documentation tooltips for WebNN API methods when properly typed