A Babel plugin that transforms named function expressions into function declarations wrapped in immediately-invoked function expressions (IIFEs) to fix problematic JScript engine bugs. This plugin ensures consistent behavior across different JavaScript engines, particularly legacy JScript implementations in older Internet Explorer versions.
npm install --save-dev babel-plugin-transform-jscript// The plugin is used via Babel configuration, not direct imports
// Plugin is automatically loaded by Babel when referenced in configuration{
"plugins": ["transform-jscript"]
}babel --plugins transform-jscript script.jsconst babel = require("babel-core");
const result = babel.transform("code", {
plugins: ["transform-jscript"]
});Input:
var IdenticalName = function IdenticalName(x) {
return x;
};
(function foo() {
});Output:
var IdenticalName = function () {
function IdenticalName(x) {
return x;
}
return IdenticalName;
}();
(function () {
function foo() {}
return foo;
})();Transforms named function expressions into safer IIFE patterns to avoid JScript engine bugs.
/**
* Babel plugin factory function that returns a plugin configuration object
* @param {Object} babel - Babel API object
* @param {Object} babel.types - Babel types utility for AST manipulation
* @returns {Object} Plugin configuration with visitor methods
*/
export default function({ types: t }) {
return {
visitor: {
FunctionExpression: {
exit(path) {
// Transform named function expressions to fix JScript bugs
}
}
}
};
}
/**
* @typedef {Object} BabelPluginObject
* @property {Object} visitor - Visitor object containing AST node handlers
* @property {Object} visitor.FunctionExpression - FunctionExpression visitor configuration
* @property {Function} visitor.FunctionExpression.exit - Exit handler for FunctionExpression nodes
*/Transformation Logic:
_ignoreUserWhitespace flag on transformed nodesPlugin Configuration:
Use Cases:
/**
* Babel API types (provided by Babel framework)
* @typedef {Object} NodePath
* @property {Object} node - The AST node being visited
* @property {Function} replaceWith - Replace the current node with a new node
*/
/**
* @typedef {Object} FunctionExpression
* @property {Object|null} id - Function identifier (null for anonymous functions)
* @property {Array} params - Function parameters
* @property {Object} body - Function body block statement
* @property {boolean} [_ignoreUserWhitespace] - Babel internal flag for whitespace handling
*/
/**
* @typedef {Object} BabelTypes
* @property {Function} callExpression - Creates a call expression AST node
* @property {Function} functionExpression - Creates a function expression AST node
* @property {Function} blockStatement - Creates a block statement AST node
* @property {Function} toStatement - Converts an expression to a statement
* @property {Function} returnStatement - Creates a return statement AST node
*/The plugin gracefully handles edge cases: