Category: JavaScript Answers

Sometimes, we want to determine the OS path separator in JavaScript.

In this article, we’ll look at how to determine the OS path separator in JavaScript.

How to determine the OS path separator in JavaScript?

To determine the OS path separator in JavaScript, we can use the path module.

For instance, we write

const path = require("path");
console.log(path.sep);

to use the path.sep property to return the path separator string for the OS that the Node app is running on.

Conclusion

To determine the OS path separator in JavaScript, we can use the path module.

Sometimes, we want to round to whole numbers in JavaScript.

In this article, we’ll look at how to round to whole numbers in JavaScript.

How to round to whole numbers in JavaScript?

To round to whole numbers in JavaScript, we can use some Math methods.

For instance, we write

const ceiling = Math.ceil(num);
const floor = Math.floor(num);
const rounded = Math.round(num);

to call Math.ceil to get the ceiling of number num.

We call Math.floor to get the floorof number num.

And we call Math.round to get num rounded with banker’s rounding.

Conclusion

To round to whole numbers in JavaScript, we can use some Math methods.

Sometimes, we want to invoke a callback at the end of a transition with D3 and JavaScript.

In this article, we’ll look at how to invoke a callback at the end of a transition with D3 and JavaScript.

How to invoke a callback at the end of a transition with D3 and JavaScript?

To invoke a callback at the end of a transition with D3 and JavaScript, we call the on method.

For instance, we write

d3.select("#myid").transition().style("opacity", "0").on("end", myCallback);

to select the element with d3.select.

Then we call transition and style to add a transition to set opacity of the element to 0.

Next, we call on with 'end' and a callback function that runs when the end event is emitted.

Then end event is emitted when the transition is done.

Conclusion

To invoke a callback at the end of a transition with D3 and JavaScript, we call the on method.

Sometimes, we want to open window and specific size on click with JavaScript.

in this article, we’ll look at how to open window and specific size on click with JavaScript.

How to open window and specific size on click with JavaScript?

To open window and specific size on click with JavaScript, we call window.open with a string that specifies the window size.

For instance, we write

window.open("http://example.com", "mywin", "width=500,height=500");

to call window.open to open http://example.com in a window that’s 500px wide by 500px high as specified with

"width=500,height=500"

Conclusion

To open window and specific size on click with JavaScript, we call window.open with a string that specifies the window size.

Sometimes, we want to get old value with onchange() event in text box with JavaScript.

In this article, we’ll look at how to get old value with onchange() event in text box with JavaScript.

How to get old value with onchange() event in text box with JavaScript?

To get old value with onchange() event in text box with JavaScript, we can get the old value when the click event is emitted.

For instance, we add an input with

<input type="text" id="test" value="ABS" oldvalue="" />

Then we write

const input = document.querySelector("input");
input.onclick = (e) => {
  e.target.setAttribute("oldvalue", e.target.vakue);
};

input.onchange = (e) => {
  e.target.setAttribute("value", e.target.getAttribute("oldvalue"));
};

to select the input with querySelector.

Then we set input.onclick to a function that gets the input value when we click it.

We get the old input value with e.target.value.

Next we set input.onchange to a function that calls e.target.setAttribute to set the value attribute to the oldvalue attribute’s value we get with getAttribute.

Conclusion

To get old value with onchange() event in text box with JavaScript, we can get the old value when the click event is emitted.