Category: JavaScript

Sometimes, we want to check if a string is JSON in JavaScript.

In this article, we’ll look at how to check if a string is JSON in JavaScript.

Check if a String is JSON in JavaScript

To check if a string is JSON in JavaScript, we can use the JSON.parse method within a try-catch block.

For instance, we can write:

const jsonStr = JSON.stringify({  
  foo: 'bar'  
})  
try {  
  const json = JSON.parse(jsonStr);  
} catch (e) {  
  console.log('invalid json');  
}

to check if jsonStr is a valid JSON string.

Since we created the JSON string by calling JSON.stringify with an object, it should be valid JSON.

Next, we have a try-catch block with the JSON.parse call in the try block to try to parse the jsonStr string with JSON.parse .

Since jsonStr is a valid JSON string, the code in the catch block shouldn’t run.

If jsonStr isn’t a valid JSON string, then the code in the catch block runs since JSON.parse will throw an exception if it’s called with an invalid JSON string.

Conclusion

To check if a string is JSON in JavaScript, we can use the JSON.parse method within a try-catch block.

Sometimes, we want to create a text input dynamically with JavaScript.

In this article, we’ll look at how to create a text input dynamically with JavaScript.

Create a Text Input Dynamically with JavaScript

To create a text input dynamically with JavaScript, we can use the document.createElement method to create the input element.

Then we can call appendChild to append the element to a container element.

For instance, we can write:

const input = document.createElement("input");  
input.type = "text";  
input.className = "css-class-name";  
document.body.appendChild(input);

We call document.createElement with 'input' to create an input element.

Then we set input.type to 'text' to set the type attribute of the created input element to 'text' .

Next, we set input.className to the value of the class attribute.

And finally, we call document.body.appendChild with input to append the input element as the last child of the HTML body element.

We can replace document.body with another container element that we want to attach the input element to as its last child.

Conclusion

To create a text input dynamically with JavaScript, we can use the document.createElement method to create the input element.

Then we can call appendChild to append the element to a container element.

Sometimes, we want to calculate x% of a number with JavaScript.

In this article, we’ll look at how to calculate x% of a number with JavaScript.

Calculate x% of a Number with JavaScript

To calculate x% of a number with JavaScript, we can divide x by 100 then multiply by the number we want to compute the percentage for.

For instance, we can write:

const x = 35.8
const result = (x / 100) * 10000;
console.log(result)

We assign the percentage number to x .

Then we divide that by 100 to get a decimal number with the fraction that we want to multiply the number with.

We multiply that by 10000 to get 35.8% of 10000 and assign that to result .

Therefore, result is 3580.

Conclusion

To calculate x% of a number with JavaScript, we can divide x by 100 then multiply by the number we want to compute the percentage for.

Sometimes, we want to style HTML5 canvas text to be bold or italic with JavaScript.

In this article, we’ll look at how to style HTML5 canvas text to be bold or italic with JavaScript.

Style HTML5 Canvas Text to be Bold or Italic with JavaScript

To style HTML5 canvas text to be bold or italic, we can set the font property of the 2d canvas context with the style of the text.

For instance, we can write the following HTML:

<canvas style='width: 200px; height: 200px'></canvas>

to add the canvas element.

Then we can write the following JavaScript:

const canvas = document.querySelector("canvas");  
const ctx = canvas.getContext("2d");  
ctx.font = "italic bold 20pt Courier";  
ctx.fillText("Hello World", 10, 50);

to get the canvas with document.querySelector .

Then we call getContext with '2d' to get the 2d canvas context.

Next, we set the font property of the returned context object with a string with the text styles.

italic makes it italic. bold makes it bold. 20pt is the text size. Courier is the font family.

Finally, we call fillText with the text that we want to display and the x and y coordinates of the top left corner of the text.

Now we should see ‘Hello World’ displayed with Courier font, bold, and italic as a result.

Conclusion

To style HTML5 canvas text to be bold or italic, we can set the font property of the 2d canvas context with the style of the text.

Sometimes, we want to exponentiate numbers with JavaScript.

In this article, we’ll look at how to exponentiate numbers with JavaScript.

Exponentiate Numbers with JavaScript

To exponentiate numbers with JavaScript, we can use the ** operator or the Math.pow method.

For instance, we can write:

const num = 2 ** 3

or:

const num2 = Math.pow(2, 3)

The first operand if ** is the base and the 2nd is the exponent.

The first argument of Math.pow is the base and the 2nd is the exponent.

As a result, we get 8 for num and num2 .

Conclusion

To exponentiate numbers with JavaScript, we can use the ** operator or the Math.pow method.