Author: John Au-Yeung

Web developer specializing in React, Vue, and front end development.

Categories
JavaScript Answers

How to insert text in a td with ID using JavaScript?

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Sometimes, we want to insert text in a td with ID using JavaScript.

In this article, we’ll look at how to insert text in a td with ID using JavaScript.

How to insert text in a td with ID using JavaScript?

To insert text in a td with ID using JavaScript, we set the innerHTML property.

For instance, we write

document.getElementById("td1").innerHTML = "Some text to enter";

to select the td element with getElementById.

Then we set its innerHTML property to the text we want to show in the td element.

Conclusion

To insert text in a td with ID using JavaScript, we set the innerHTML property.

Categories
JavaScript Answers

How to listen for the click event for a marker in Leaflet?

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Sometimes, we want to listen for the click event for a marker in Leaflet.

In this article, we’ll look at how to listen for the click event for a marker in Leaflet.

How to listen for the click event for a marker in Leaflet?

To listen for the click event for a marker in Leaflet, we can use the on method.

For instance, we write

L.marker([10.496093, -66.881935])
  .addTo(map)
  .on("click", (e) => {
    console.log(e.latlng);
  });

to call L.marker with an array with the longitude and latitude to create a marker.

Then wee call addTo to add it to the map.

And then we call on to add a click listener.

In the click listener, we get the latitude and longitude with e.latlng.

Conclusion

To listen for the click event for a marker in Leaflet, we can use the on method.

Categories
Angular Answers

How to call a method in the child component with Angular?

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Sometimes, we want to call a method in the child component with Angular.

In this article, we’ll look at how to call a method in the child component with Angular.

How to call a method in the child component with Angular?

To call a method in the child component with Angular, we can use ViewChild.

For instance, we write

@Component({
  // ...
})
export class Parent {
  @ViewChild(Child) child: Child;

  incrementSonBy5() {
    this.child.updateData(this.child.data + 5);
  }
}

to create the Parent component.

We reference the Child component with @ViewChild(Child) child: Child;.

Then we get the properties and methods in Child with this.child.

Next, we add the Child component with

@Component({
  // ...
  template: `{{ data }}`,
  // ...
})
export class Child {
  data: number = 3;

  constructor() {}

  updateData(data: number) {
    this.data = data;
  }
}

We add the data property and the updateData component method that were referenced in Parent.

Conclusion

To call a method in the child component with Angular, we can use ViewChild.

Categories
JavaScript Answers

How to remove a child node in HTML using JavaScript?

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Sometimes, we want to remove a child node in HTML using JavaScript.

In this article, we’ll look at how to remove a child node in HTML using JavaScript.

How to remove a child node in HTML using JavaScript?

To remove a child node in HTML using JavaScript, we can use the remove method.

For instance, we write

document.getElementById("FirstDiv").remove();

to select the element with getElementById.

Then we call remove to remove the selected element.

Conclusion

To remove a child node in HTML using JavaScript, we can use the remove method.

Categories
JavaScript Answers

How to check whether a variable is defined in Node.js and JavaScript?

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Sometimes, we want to check whether a variable is defined in Node.js and JavaScript.

In this article, we’ll look at how to check whether a variable is defined in Node.js and JavaScript.

How to check whether a variable is defined in Node.js and JavaScript?

To check whether a variable is defined in Node.js and JavaScript, we can check if it’s not null or undefined.

For instance, we write

if (typeof query !== "undefined" && query !== null) {
  doStuff();
}

to check if query isn’t undefined with typeof query !== "undefined".

And we check if query isn’t null with query !== null.

Conclusion

To check whether a variable is defined in Node.js and JavaScript, we can check if it’s not null or undefined.