helpers


Install

 sh
npm install --save-dev @babel/helpers

Usage

Direct:

 js
import * as helpers from '@babel/helpers';
import * as t from '@babel/types';

const typeofHelper = helpers.get('typeof');

t.isExpressionStatement(typeofHelper);
// true

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Inside a plugin:

 js
export default {
  visitor: {
    UnaryExpression(path) {
      // The .addHelper function adds, if needed, the helper to the file
      // and returns an expression which references the helper
      const typeofHelper = this.addHelper("typeof");
      t.isExpression(typeofHelper); // true
  }
};

Defining Helpers

NOTE: This package is only meant to be used by the packages included in this repository. There is currently no way for third-party plugins to define a helper.

Helpers are defined in the src/helpers.js file, and they must be valid modules which follow these guidelines:

  • They must have a default export, which is their entry-point.
  • They can import other helpers, exclusively by using default imports.
  • They can’t have named exports.
helpers.customHelper = defineHelper(`
  import dep from "dependency";

  const foo = 2;

  export default function getFooTimesDepPlusX(x) {
    return foo * dep() + x;
  }
`);

← code-frameruntime →

来源:Js中文网 – 前端进阶资源教程
链接:https://www.javascriptc.com/docs/babel-manual/babel-helpers

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