Converts underscore/lodash `.each()` with context to use Function.prototype.bind()

each-with-context-to-bind.js

/**
 * Converts underscore/lodash `.each()` with context to use Function.prototype.bind()
 *
 * Run this with jscodeshift
 * Live demo: https://astexplorer.net/#/gist/b4294e95ef898af1d19cd3db19f9e8b0/latest
 *
 * Converts:
 *     _.each(array, function(item) {
 *       // ...
 *     }, context);
 *
 * to:
 *     _.each(array, function(item) {
 *       // ...
 *     }.bind(context));
 */

module.exports = function transformer(file, api) {
  const j = api.jscodeshift;

  return j(file.source)
    .find(j.CallExpression)
    .filter(
      path =>
        path.node.callee.type === "MemberExpression" &&
        path.node.callee.object.type === "Identifier" &&
        path.node.callee.object.name === "_" &&
        path.node.callee.property.type === "Identifier" &&
        path.node.callee.property.name === "each" &&
        path.node.arguments.length === 3 &&
        path.node.arguments[1] &&
        path.node.arguments[2]
    )
    .forEach(path => {
      let iterator = path.node.arguments[1];
      let context = path.node.arguments[2];
      path.node.arguments.length = 2;
      path.node.arguments[1] = j.callExpression(
        j.memberExpression(iterator, j.identifier("bind")),
        [context]
      );
    })
    .toSource();
};