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tessl/npm-babel-helper-optimise-call-expression

Helper function to optimize call expressions by choosing between apply() and call() methods for Babel transformations

Workspace
tessl
Visibility
Public
Created
Last updated
Describes
npmpkg:npm/babel-helper-optimise-call-expression@6.24.x

To install, run

npx @tessl/cli install tessl/npm-babel-helper-optimise-call-expression@6.24.0

index.mddocs/

babel-helper-optimise-call-expression

babel-helper-optimise-call-expression is a utility function for optimizing function call expressions in JavaScript AST transformations. It intelligently chooses between Function.prototype.apply() and Function.prototype.call() patterns to generate optimal call expressions for Babel plugins and transformers.

Package Information

  • Package Name: babel-helper-optimise-call-expression
  • Package Type: npm
  • Language: JavaScript
  • Installation: npm install babel-helper-optimise-call-expression

Core Imports

import optimiseCallExpression from "babel-helper-optimise-call-expression";

For CommonJS:

const optimiseCallExpression = require("babel-helper-optimise-call-expression");

Basic Usage

import optimiseCallExpression from "babel-helper-optimise-call-expression";
import * as t from "babel-types";

// Example usage in a Babel plugin
function transformMethodCall(path) {
  const callee = t.identifier("methodName");
  const thisNode = t.identifier("obj");
  const args = [t.stringLiteral("arg1"), t.numericLiteral(42)];
  
  // Generates optimized call expression
  const optimizedCall = optimiseCallExpression(callee, thisNode, args);
  // Result: methodName.call(obj, "arg1", 42)
  
  path.replaceWith(optimizedCall);
}

// Example with spread arguments
function transformSpreadCall(path) {
  const callee = t.identifier("super");
  const thisNode = t.thisExpression();
  const args = [t.spreadElement(t.identifier("arguments"))];
  
  // Generates apply() call for spread arguments pattern
  const optimizedCall = optimiseCallExpression(callee, thisNode, args);
  // Result: super.apply(this, arguments)
  
  path.replaceWith(optimizedCall);
}

Capabilities

Call Expression Optimization

Optimizes function call expressions by choosing the most appropriate calling pattern based on the provided arguments.

/**
 * Optimizes function call expressions by choosing between apply() and call() patterns
 * @param {ASTNode} callee - The function/method being called (AST node)
 * @param {ASTNode} thisNode - The context/this value for the call (AST node)
 * @param {ASTNode[]} args - Array of argument expressions (Array of AST nodes)
 * @returns {CallExpression} Optimized call expression AST node
 */
function optimiseCallExpression(callee, thisNode, args);

Optimization Logic:

  1. Spread Arguments Pattern: When args contains a single spread element with the identifier arguments, generates callee.apply(thisNode, arguments)
  2. Regular Arguments Pattern: For all other cases, generates callee.call(thisNode, ...args)

Parameters:

  • callee: The function or method being called, represented as a babel-types AST node
  • thisNode: The context object or this value for the function call, as a babel-types AST node
  • args: Array of argument expressions as babel-types AST nodes

Returns:

A t.callExpression AST node using either the .apply() or .call() pattern depending on the arguments provided.

Usage Examples:

import optimiseCallExpression from "babel-helper-optimise-call-expression";
import * as t from "babel-types";

// Case 1: Regular arguments -> call() pattern
const regularCall = optimiseCallExpression(
  t.identifier("fn"),
  t.thisExpression(),
  [t.stringLiteral("hello"), t.numericLiteral(42)]
);
// Generates: fn.call(this, "hello", 42)

// Case 2: Spread arguments -> apply() pattern
const spreadCall = optimiseCallExpression(
  t.identifier("fn"),
  t.thisExpression(),
  [t.spreadElement(t.identifier("arguments"))]
);
// Generates: fn.apply(this, arguments)

// Case 3: Method call optimization
const methodCall = optimiseCallExpression(
  t.memberExpression(t.identifier("obj"), t.identifier("method")),
  t.identifier("context"),
  [t.identifier("arg1"), t.identifier("arg2")]
);
// Generates: obj.method.call(context, arg1, arg2)

// Case 4: Real usage in babel-helper-replace-supers
class ReplaceSupers {
  optimiseCall(callee, args) {
    const thisNode = t.thisExpression();
    return optimiseCallExpression(callee, thisNode, args);
  }
}

Types

This package works with babel-types AST nodes. Key types include:

// Input parameter types (from babel-types)
interface ASTNode {
  type: string;
}

interface CallExpression extends ASTNode {
  type: "CallExpression";
  callee: ASTNode;
  arguments: ASTNode[];
}

interface MemberExpression extends ASTNode {
  type: "MemberExpression";
  object: ASTNode;
  property: ASTNode;
}

interface SpreadElement extends ASTNode {
  type: "SpreadElement";
  argument: ASTNode;
}

interface Identifier extends ASTNode {
  type: "Identifier";
  name: string;
}

Dependencies

This package has the following dependencies:

  • babel-runtime: ^6.22.0 - Babel runtime helpers
  • babel-types: ^6.24.1 - Utilities for AST node creation and type checking

The function uses several babel-types utilities:

  • t.callExpression() - Creates function call expressions
  • t.memberExpression() - Creates property/method access expressions
  • t.identifier() - Creates identifier nodes
  • t.isSpreadElement() - Type checker for spread elements
  • t.isIdentifier() - Type checker for identifiers

Use Cases

This helper is designed for use within:

  • Babel Plugins: Transform function calls in JavaScript code during compilation
  • AST Transformations: Optimize call patterns in abstract syntax tree manipulations
  • Code Generation: Generate efficient call expressions in transpiled or generated code
  • Method Call Optimization: Ensure proper this binding in transformed method calls
  • Performance-Critical Calls: Optimize function invocation patterns for better runtime performance