Category: JavaScript Answers

Sometimes, we want to parse Excel (XLS) file in JavaScript and HTML5.

In this article, we’ll look at how to parse Excel (XLS) file in JavaScript and HTML5.

How to parse Excel (XLS) file in JavaScript and HTML5?

To parse Excel (XLS) file in JavaScript and HTML5, we can use the read-excel-file library.

To install it, we run

npm install read-excel-file --save

Then we write

import readXlsxFile from "read-excel-file";

const input = document.getElementById("input");

input.addEventListener("change", async () => {
  const data = await readXlsxFile(input.files[0]);
});

to select the input with getElementById

Then we call addEventListener on it with 'change' and a callback that calls readXlsxFile to read the select file.

We get the read data from data which is an array of rows with each row being an array of cells.

Conclusion

To parse Excel (XLS) file in JavaScript and HTML5, we can use the read-excel-file library.

Sometimes, we want to format date and subtract days using Moment.js and JavaScript.

In this article, we’ll look at how to format date and subtract days using Moment.js and JavaScript.

How to format date and subtract days using Moment.js and JavaScript?

To format date and subtract days using Moment.js and JavaScript, we call format to format dates and subtract to subtract days.

For instance, we write

let startdate = moment();
startdate = startdate.subtract(1, "days");
startdate = startdate.format("DD-MM-YYYY");

to call subtract to subtract 1 day from the current date.

And then we call format to return a date string in DD-MM-YYYY format.

Conclusion

To format date and subtract days using Moment.js and JavaScript, we call format to format dates and subtract to subtract days.

Sometimes, we want to unit test a Node.js module that requires other modules and how to mock the global require function.

In this article, we’ll look at how to unit test a Node.js module that requires other modules and how to mock the global require function.

How to unit test a Node.js module that requires other modules and how to mock the global require function?

To unit test a Node.js module that requires other modules and how to mock the global require function, we can use proxyquire.

To install it, we run

npm i proxyquire

Then we use it by writing

const proxyquire = require("proxyquire");
const assert = require("assert");
const pathStub = {};

//...

const foo = proxyquire("./foo", { path: pathStub });
assert.strictEqual(foo.bar("file.txt"), ".TXT");

to call proxyquire with the path to the module.

Then we call foo.bar from the foo module and check its returned value.

Conclusion

To unit test a Node.js module that requires other modules and how to mock the global require function, we can use proxyquire.

Sometimes, we want to capture key press or keydown event on a div element with JavaScript.

In this article, we’ll look at how to capture key press or keydown event on a div element with JavaScript.

How to capture key press or keydown event on a div element with JavaScript?

To capture key press or keydown event on a div element with JavaScript, we listen to the keyup event.

For instance, we write

document.querySelector("#myDiv").addEventListener("keyup", (e) => {
  console.log(e.key);
});

to select the div with document.querySelector("#myDiv").

Then we call addEventListener on it with 'keyup' and a function that runs when we release the key that’s pressed.

In it, we get the key released with e.key.

Conclusion

To capture key press or keydown event on a div element with JavaScript, we listen to the keyup event.

Sometimes, we want to add line breaks to an HTML textarea with JavaScript.

In this article, we’ll look at how to add line breaks to an HTML textarea with JavaScript.

How to add line breaks to an HTML textarea with JavaScript?

To add line breaks to an HTML textarea with JavaScript, we can add '\r\n' to the string.

For instance, we write

const txtArea = document.getElementById("txt");
txtArea.value += text + "\r\n";

to select the text area with getElementById.

And then we append text + "\r\n" to the value property.

"\r\n" adds the line breaks.

Conclusion

To add line breaks to an HTML textarea with JavaScript, we can add '\r\n' to the string.