Code mod for adding use strict to file

addUseStrict.js

module.exports = function(file, api){
  var j = api.jscodeshift;
  var root = j(file.source);
  var useStrict = '"use strict";';

  var hasUseStrict = root.find(j.ExpressionStatement,{
    expression: {
      type: 'Literal',
      value: 'use strict',
    },
  });

  if(hasUseStrict.length === 0){
    root.get().node.program.body.unshift(useStrict);
  }

  return root.toSource();
}