How can I get my content hash code to work?

I’m following this https://www.youtube.com/watch?v=MpGLUVbqoYQ webpack tutorial precisely, and have gotten to the part of the video where he talks about content hashing. On the video he does:

    const path = require("path");
    module.exports = {
      mode: "development",
      entry: "./src/index.js",
      output: {
        filename: "main.[contentHash].js",
        path: path.resolve(__dirnamem, "dist")
      },
      module: {
        rules: [
          {
            test: /.scss$/,
            use: [
              "style-loader",
              "css-loader",
              "sass-loader"
            ]
          }
        ]
      }
    };

I have done:

const path = require("path");

module.exports =  {
    mode: "development",
    entry: "./src/index.js",
    output: {
        filename: "main.[contentHash].js",
        path: path.resolve(__dirname, "dist")
    },
    module: {
        rules: [
            {
                test: /.scss$/,
                use: [
                    "style-loader", // 3. Injects styles into DOM
                    "css-loader",  // 2. Turns css into commonjs
                    "sass-loader" // 1. Turns sass into css
                ]
            }
        ]
    }
};

On the video this code works and appends a content hash where indicated, but when I ran npm start, I got this: