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Javascript Articles
Page 184 of 534
How to transform a String into a function in JavaScript?
We have given a string and need to convert it into a function in JavaScript. Sometimes, we get mathematical or function expressions in the form of the string, and executing that expression, requires converting strings into the function expression. In this tutorial, we will learn different approaches to converting the given string into a functional or mathematical expression. Use the eval() method The eval() method takes the expression as a parameter and evaluates the expression. For example, if we pass the ‘2 + 2’ string as a parameter of the eval() method, it returns 4 as it evaluates the ...
Read MoreHow to transform a JavaScript iterator into an array?
In JavaScript, the iterator is a collection of elements through which we can iterate and access a single element every iteration. The set, map, or object is an iterator in JavaScript, and we can’t access the elements of the iterator using the index like the array. So, we first require to convert the iterator into the array. Here, we will use different methods like an array.from(), etc., to convert an iterator to the array. Use the for-of loop The for-of loop iterates through every element of the iterator lie set and map. Inside the for-of loop, we can ...
Read MoreHow to skip over an element in .map()?
In JavaScript, we sometimes require to skip array elements while using the map() method. For example, we need to map value from one array to another array after performing some mathematical operations on the element only if the array value is finite. In such cases, users can use the below approaches to skip over array elements while using the map() method. Use the if-else statement In the array.map() method, we can use the if-else statement to skip over the element. If the element fulfills the if-else statement condition, we need to return the element for mapping; Otherwise, we ...
Read MoreHow to zoom in and zoom out images using JavaScript?
The zoom-in and zoom out is an important functionality for the image. We can see every single information of the image by zoom-in. Maybe, you can press the ‘ctrl’ and ‘+’ keys together to zoom in to your browser, and you can see everything looks bigger in the browser window. The zoom-in feature is useful for reading small texts on the screen also. So, there can be various use cases of zoom in and zoom out. In this tutorial, we will learn to zoom in and zoom out images using JavaScript. Use the height and width properties to ...
Read MoreHow to validate email address using RegExp in JavaScript?
Anyone can make a mistake while entering the email in the input field. So, it’s the developer's responsibility to check if users have entered a valid email string. Many libraries are available to validate email addresses, which we can use with various JavaScript frameworks, but not with vanilla JavaScript. However, if we want to use any library, we need to use its CDN. Here, we will use the regular expression to validate the email address in vanilla JavaScript. Regex Used in Example 1 We have used the below regular expression pattern in example 1 to validate the email. let ...
Read MoreHow to validate an input is alphanumeric or not using JavaScript?
We have been given the task of validating the input string and need to check whether it is alphanumeric or not using JavaScript. The alphanumeric string contains only numeric and alphabetical characters, including uppercase or lowercase characters, and even it doesn’t contain any special characters or spaces. Below, we will see two approaches to validate an input string. Use the charCodeAt() method We can use the charCodeAT() method to get the ASCII value of any character. Here, we will iterate through every character of the string and check the ASCII value of every character. The ASCII code between 48 ...
Read MoreHow to use map() on an array in reverse order with JavaScript?
We have given the array of elements and need to use the map() on the array in reverse order with JavaScript. The map() method maps the new element related to a particular array element in the resultant array. Sometimes, we require to map the elements in reverse order. There can be many ways to use map() on an array in reverse order. We will see all approaches one by one. Introduction to map() method Syntax Follow the syntax below to use the map() method. array.map((ele, ind, array) => { return ele + 20; }) ...
Read MoreHow to use map and filter simultaneously on an array using JavaScript?
The filter() method is used to filter values from the array, and the map() method is used to map a new value to another array based on every value of the old array. Sometimes, we require to use the filter() and map() methods together. For example, we wanted to filter all positive numbers from the array and map their logarithmic value to the new array Let’s look at the introduction of the filter() and map() methods before we start with this tutorial. In this tutorial, we will learn to use the map and filter methods simultaneously on an array ...
Read MoreHow to use the JavaScript function in the check box?
While working with the HTML checkboxes, sometimes developers may require to use the checkboxes to allow users to select multiple options. Also, developers need to perform some actions based on the selected checkbox. For example, you have given the checkbox with a question like are you above 18? If users check this checkbox, only show the input to take a user’s pan card number. So, we need to call a function whenever the user checks and unchecks the checkboxes. Use the onchange event The onchange event attribute allows us to invoke a function whenever the user checks and ...
Read MoreHow to unpack array elements into separate variables using JavaScript?
Unpacking array elements means assigning array element values to the new variables. We can assign every element to the separate variables, or we can assign some elements to the separate variables, and for the remaining elements, we can create a new array. In this tutorial, we will learn to unpack array elements into separate variables using JavaScript. Syntax Users can follow the syntax below to unpack the array elements into separate variables. let array = [element1, element2, element3, element4]; let [a, b, c, d] = array; In the above syntax, a variable contains the value of element1, ...
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