Category: JavaScript Answers

Sometimes, we want to pipe the same readable stream into multiple writable targets with Node.js and JavaScript.

In this article, we’ll look at how to pipe the same readable stream into multiple writable targets with Node.js and JavaScript.

How to pipe the same readable stream into multiple writable targets with Node.js and JavaScript?

To pipe the same readable stream into multiple writable targets with Node.js and JavaScript, we can use the PassThrough object.

For instance, we write

const spawn = require("child_process").spawn;
const PassThrough = require("stream").PassThrough;

const a = spawn("echo", ["hi user"]);
const b = new PassThrough();
const c = new PassThrough();

a.stdout.pipe(b);
a.stdout.pipe(c);

let count = 0;
b.on("data", (chunk) => {
  count += chunk.length;
});
b.on("end", () => {
  console.log(count);
  c.pipe(process.stdout);
});

to create PassThrough objects b and c.

Then we call a.stdout.pipe with them to pipe them to b and c.

Next we listen for data events on b to get the chunks.

And then when the end event is triggered on b, we call c.pipe with process.stdout to pipe process.stdout to c.

Conclusion

To pipe the same readable stream into multiple writable targets with Node.js and JavaScript, we can use the PassThrough object.

Sometimes, we want to play sound notifications using JavaScript.

In this article, we’ll look at how to play sound notifications using JavaScript.

How to play sound notifications using JavaScript?

To play sound notifications using JavaScript, we can use the audio element’s play method.

For instance, we write

document.getElementById("yourAudioTag").play();

to get the audio element with getElementById.

Then we call play on it to start playing the sound.

Conclusion

To play sound notifications using JavaScript, we can use the audio element’s play method.

Sometimes, we want to get the ID of element that called a function with JavaScript.

In this article, we’ll look at how to get the ID of element that called a function with JavaScript.

How to get the ID of element that called a function with JavaScript?

To get the ID of element that called a function with JavaScript, we can use the evt.target.id property.

For instance, we write

document.getElementById("preview").onmouseover = (evt) => {
  console.log(evt.target.id);
};

to get the element with getElementById.

Then we set its onmouseover property to a function that runs when we move our mouse over the element.

In it, we use evt.target.id to get the ID of the element that we moved our mouse over.

Conclusion

To get the ID of element that called a function with JavaScript, we can use the evt.target.id property.

Sometimes, we want to get background image URL of an element using JavaScript.

In this article, we’ll look at how to get background image URL of an element using JavaScript.

How to get background image URL of an element using JavaScript?

To get background image URL of an element using JavaScript, we use the getComputedStyle method.

For instance, we write

const img = document.getElementById("id");
const style = window.getComputedStyle(img, false);
const bi = style.backgroundImage.slice(4, -1).replace(/"/g, "");

to get the element with getElementById.

Then we call getComputedStyle to get the computed styles of the element as an object.

Then we write style.backgroundImage.slice(4, -1).replace(/"/g, "") to get the background image URL.

Conclusion

To get background image URL of an element using JavaScript, we use the getComputedStyle method.

Sometimes, we want to stub a method of Jasmine mock object with JavaScript.

In this article, we’ll look at how to stub a method of Jasmine mock object with JavaScript.

How to stub a method of Jasmine mock object with JavaScript?

To stub a method of Jasmine mock object with JavaScript, we can use the callFake method.

For instance, we write

const someObject = jasmine.createSpyObj("someObject", ["method1", "method2"]);

const error = new Error("an-exception");
someObject.method1.and.callFake(() => {
  throw error;
});
expect(yourFncCallingMethod1).toThrow(error);

to call createSpyObj to create a spy object.

Then we call someObject.method1.and.callFake with a function with the mocked implementation of method1.

Then we check that the yourFncCallingMethod1 function which calls method1 to throw an error.

Conclusion

To stub a method of Jasmine mock object with JavaScript, we can use the callFake method.

Conclusion

To stub a method of Jasmine mock object with JavaScript, we can use the callFake method.