A jscodeshift transformer to make classes from Backbone extends declarations

backboneToClass.js

// Transform backbone declaration to class
// follows https://github.com/jashkenas/backbone/issues/3560#issuecomment-248670605
export default function transformer(file, api) {
  const j = api.jscodeshift;

  return j(file.source)
    .find(j.VariableDeclaration)
    .filter((path)=>{
      var decl = path.node.declarations[0];
      var init = decl.init;
      return init && init.type=='CallExpression' && init.callee.property && init.callee.property.name=='extend' && init.callee.object && init.callee.object.name != '_' && init.callee.object.name != '$';
    }).replaceWith((path) => {
      var decl = path.node.declarations[0];
      var init = decl.init;
    	const name = decl.id;
      var superclass = init.callee.object;
      const content = init.arguments[0];
      const methods = [];
      const initvars = [];
      for (var val of content.properties) {
        if (val.value.type == 'FunctionExpression') {
          const isCons = val.key.name == 'constructor';
          const method = j.methodDefinition(isCons?'constructor': 'method', j.literal(val.key.name), val.value, false);
          method.comments = val.comments;
          methods.push(method);
        } else {
          initvars.push(val);
        }
      }
    	if (initvars.length > 0) {
        superclass = j.callExpression(
          j.memberExpression(superclass, j.identifier('extend'), false),
          [j.objectExpression(initvars)]);
      }
      const cls = j.classDeclaration(name, j.classBody(methods), superclass);
    	cls.comments = path.node.comments;
	    return cls;
    }).toSource();
}