Javascript Articles - Page 346 of 607

The eval() function in JavaScript allows the execution of code stored as a string. It can be used to fetch specific values dynamically, but be careful, as it can have security risks and affect performance. This article will guide you on how to use eval() to get specific values and why you should generally avoid using eval(). How eval() Works? The eval() function takes a string as an argument and evaluates it as JavaScript code. For example: console.log(eval("2 + 2")); // Output: 4 Fetching Specific Values Using eval() The eval() function in JavaScript can be used to: ... Read More

For this, use a “prototype”. JavaScript objects inherit properties and methods from a prototype. For accessing variables, we have also used the “this” in JavaScript.Examplefunction Customer(fullName){    this.fullName=fullName; } Customer.prototype.setFullName = function(newFullName){    this.fullName=newFullName; } var customer=new Customer("John Smith"); console.log("Using Simple Method = "+ customer.fullName); customer.setFullName("David Miller"); console.log("Using Prototype Method = "+customer.fullName);To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo79.js.OutputThis will produce the following output −PS C:\Users\Amit\JavaScript-code> node demo79.js Using Simple Method = John Smith Using Prototype Method = David MillerRead More

Let’s say the following is our Unordered List (ul) −    JavaScript Remove        MySQL Remove        MongoDB Remove        Java Remove Above, you can see the “Remove” button with every li element. On clicking this button, you can remove any li element.Following is the code to remove li elements on button click;Example Live Demo Document Remove the subjects The Subjects are as follows: JavaScript Remove MySQL Remove MongoDB Remove Java Remove    var allSubjectName = document.querySelectorAll(".subjectName");    for (var index = 0; index

You can use the concept of Map(). In JavaScript, map has the key value concept in which key must be unique.We also need to use the join() method to join Map values. Following is the code −Examplelet queryStringAppendWithURL = new Map(); queryStringAppendWithURL.set("firstParamter", ["name=John", "age=23", "countryName=US"]); queryStringAppendWithURL.set("secondParamter", ["subjectName=JavaScript", "Marks=91"]); let appendValue = Array.from(queryStringAppendWithURL.values()).map(value => value.join('?')).join('?'); console.log("The appended value is="+appendValue);To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo78.js.OutputThis will produce the following output −PS C:\Users\Amit\JavaScript-code> node demo78.js The appended value is=name=John?age=23?countryName=US?subjectName=JavaScript?Marks=91Read More

To conditionally change object property, use the logical AND operator ( &&).If both the operands are non-zero, then the condition becomes true in JavaScript’s logical AND operator.Examplelet marksDetails = { Mark1: 33, Mark2: 89 }, isBacklog = false; console.log("Result when backlog is set to false==="); console.log({ ...marksDetails, ...isBacklog === true && { Mark1: 33 }}); isBacklog = true; console.log("Result when backlog is set to true==="); console.log({ ...marksDetails, ...isBacklog === true && { Mark1: 93 }});To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo77.js.OutputThis will produce the following output −PS C:\Users\Amit\JavaScript-code> ... Read More

To remove leading zeroes in an array, use the concept of filter(). Following is our input wherein we will remove the leading zeroes −[10,0,12,0,0]) [0,0,0,0,0,0,10,12,0]) [12,0,0,1,0,0])Exampleconst removeLeadingZero = input => input.filter((lastValue => value => lastValue= lastValue || value) (false) ); console.log(removeLeadingZero([10,0,12,0,0])); console.log(removeLeadingZero([0,0,0,0,0,0,10,12,0])); console.log(removeLeadingZero([12,0,0,1,0,0]));To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo76.js.OutputThis will produce the following output −PS C:\Users\Amit\JavaScript-code> node demo76.js [ 10, 0, 12, 0, 0 ] [ 10, 12, 0 ] [ 12, 0, 0, 1, 0, 0 ]

To change value of input, use the concept of document. The syntax is as follows −document.yourFormName.yourTextName.value=anyValue;Let’s say the following is our input type calling submitForm() on clicking “Submit Form” −         The submitForm() function changing the value of input −function submitForm(){    document.studentForm.txtInput.value='STUDENT-100'; }Example Live Demo Document    function submitForm(){       document.studentForm.txtInput.value='STUDENT-100';    } To run the above program, save the file name “anyName.html(index.html)” and right click on the file. Select the option “Open with Live Server” in ... Read More

If onclick not working for two or more links, then use the document.querySelectorAll() in JavaScript. Following is the code −Example Live Demo Document www.example.com www.test.com    const values = document.querySelectorAll('[class=class1]');    values.forEach(function(v) {       console.log(v.innerHTML);    }); To run the above program, save the file name “anyName.html(index.html)” and right click on the file. Select the option “Open with Live Server” in VS Code editor.OutputThis will produce the following output −

To check if the input is a number or letter, use the isNaN() function from JavaScript. It returns true if the value is NaN i.e. Not a Number. Following is the code −Example Live Demo Document Enter the value:    function checkInputIsNumber(){       var value=document.forms["checkingInput"]["txtValue"].value;       if (isNaN(value)){          alert("Please Provide the input as a number");          return false;       }    } To run the above program, save the file ... Read More

To check if array element contains a false value, you can use the Object.values() in JavaScript. Following is the code −Exampleconst details = [    {       customerDetails:       [          {             isMarried: true          },          {             isMarried: true          }       ]    },    {       customerDetails:    [       {             isMarried: true          },          {          isMarried: true          }       ]    } ] const isNotMarried = Object.values(details) .some(({customerDetails})=>customerDetails.some(({isMarried})=>!isMarrie d)); console.log(isNotMarried);To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo75.js.OutputThis will produce the following output −PS C:\Users\Amit\JavaScript-code> node demo75.js false