I am trying to build a react app but each time I run npm start, I am greeted with this message

Module not found: Error: Can't resolve 'buffer' in '/Users/abdus/Documents/GitHub/keywords-tracker/node_modules/buffer-equal-constant-time'

BREAKING CHANGE: webpack < 5 used to include polyfills for node.js core modules by default. This is no longer the case. Verify if you need this module and configure a polyfill for it.

It gives the same message for a few different modules. I have tried npm installing these modules but the error persists

CodePudding user response：

this is my webpack set up that works. you should install all the packages that listed in fallback:

// const path = require("path");
const path = require("path");
const HtmlWebpackPlugin = require("html-webpack-plugin");
const CopyWebpackPlugin = require("copy-webpack-plugin");
const webpack = require("webpack");

module.exports = {
  mode: "development",
  target: "web",
  entry: ["regenerator-runtime/runtime", "./src/index.js"],
  output: {
    filename: "bundle.js",
    path: path.join(__dirname, "dist"),
    publicPath: "/",
  },
  resolve: {
    extensions: [".js", ".css"],
    alias: {
      // add as many aliases as you like!
      components: path.resolve(__dirname, "src/components"),
    },
    fallback: {
      // path: require.resolve("path-browserify"),
      fs: false,
      assert: require.resolve("assert/"),
      os: require.resolve("os-browserify/browser"),
      constants: require.resolve("constants-browserify"),
      stream: require.resolve("stream-browserify"),
      crypto: require.resolve("crypto-browserify"),
      http: require.resolve("stream-http"),
      https: require.resolve("https-browserify"),
    },
  },
  // devtool: "eval-cheap-source-map",
  devtool: "eval",
  module: {
    rules: [
      { test: /\.(js|jsx)/, loader: "babel-loader", exclude: /node_modules/ },
      { test: /\.css$/, use: ["style-loader", "css-loader"] },
      //   {
      //     test: /\.m?js/,
      //     resolve: {
      //         fullySpecified: false
      //     }
      // },
      {
        test: /\.(woff(2)?|ttf|eot|jpg|jpeg|png|gif)(\?v=\d \.\d \.\d )?$/,
        use: [
          {
            loader: "file-loader",
            options: {
              name: "[name].[contenthash].[ext]",
              outputPath: "fonts/",
            },
          },
        ],
      },
      {
        test: /\.svg$/,
        use: [
          {
            loader: "svg-url-loader",
            options: {
              limit: 10000,
            },
          },
        ],
      },
      {
        test: /\.json5$/i,
        loader: "json5-loader",
        type: "javascript/auto",
        options: {
          esModule: true,
        },
      },
    ],
  },
  devServer: {
    contentBase: path.join(__dirname, "build"),
    historyApiFallback: true,
    overlay: true,
  },

  plugins: [
    new HtmlWebpackPlugin({
      title: "NFT",
      template: "src/index.html",
    }),
    // new CopyWebpackPlugin({
    //   patterns: [{ from: "assets", to: "assets" }],
    // }),
    new webpack.ProvidePlugin({
      process: "process/browser",
      Buffer: ["buffer", "Buffer"],
      React: "react",
    }),
  ],
};

you can get this webpack5-Boilerplate

CodePudding user response：

It seems like you are using a front-end react app and some dependency is internally using the buffer module which is only available in target: node under webpack. So you will need to add a polyfill for the same.

module.exports = {
   resolve: {
       fallback: {
           buffer: require.resolve('buffer'),
       }
   },
}

You can check the docs here at webpack: https://webpack.js.org/configuration/resolve/#resolvefallback

From Webpack 5 onwards, webpack doesn't polyfill for browser-based applications.