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JavaScript Answers

How to convert an image to a base64-encoded data URL in sails.js or generally in the server side JavaScript?

To convert an image to a base64-encoded data URL in sails.js or generally in the server side JavaScript, we use the buffer toString method.

For instance, we write

const fs = require("fs");

const base64Encode = (file) => {
  const bitmap = fs.readFileSync(file);
  return new Buffer(bitmap).toString("base64");
};
const base64str = base64Encode("kitten.jpg");

to define the base64Encode function.

In it, we call readFileSync to read the file.

And then we create a Buffer with the returned file binary.

Then we call toString to convert the buffer to a base64 string.

Categories
JavaScript Answers

How to fetch/scan all items from AWS dynamodb using Node.js?

To fetch/scan all items from AWS dynamodb using Node.js, we use the scan method.

For instance, we write

const scanTable = async (tableName) => {
  const params = {
    TableName: tableName,
  };

  const scanResults = [];
  const items;
  do {
    items = await documentClient.scan(params).promise();
    items.Items.forEach((item) => scanResults.push(item));
    params.ExclusiveStartKey = items.LastEvaluatedKey;
  } while (typeof items.LastEvaluatedKey !== "undefined");

  return scanResults;
};

to call scan to scan the database.

We call promise to return a promise.

And we use await to get the results.

We use items.Items to get the items returned.

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JavaScript Answers

How to use Node Sequelize findOne to find the latest entry?

To use Node Sequelize findOne to find the latest entry, we order the result by createdAt in descending order.

For instance, we write

model.findOne({
  where: { key },
  order: [["createdAt", "DESC"]],
});

to call findOne with order set to an array [["createdAt", "DESC"]] to order the result by createdAt in descending order to get the latest result.

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JavaScript Answers

How to use pipe() in Node.js net?

To use pipe() in Node.js net, we call the on method.

For instance, we write

const net = require("net");

net.createServer((socket) => {
  socket.write("Echo server\r\n");
  socket.on("data", (chunk) => {
    socket.write(chunk);
  });
  socket.on("end", socket.end);
});

to call createServer to create a server.

We call write to write a message.

And we call on to listen for data.

Categories
JavaScript Answers

How to display binary data as image in React?

To display binary data as image in React, we set the src prop to a base string.

For instance, we write

const data =
  "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";

const Example = ({ data }) => <img src={`data:image/jpeg;base64,${data}`} />;

ReactDOM.render(<Example data={data} />, document.getElementById("container"));

to set the src prop of the img element to a base64 string with the image content.