Front End Technology Articles - Page 295 of 652

We know that there are two ways we can access nested keys within an Object in JavaScript.For instance, take this object −const obj = {    object: {       foo: {          bar: {             ya: 100          }       }    } };If we needed to access or update the nested property 'ya', we can access it like −Way 1 −obj['object']['foo']['bar']['ya']orWay 2 −obj.object.foo.bar.yaBoth these ways lead us to the same destination.We are required to write a JavaScript function that takes in the path to ... Read More

Suppose, we have an array of objects like this −const arr = [    {       "customer": "Customer 1",       "project": "1"    },    {       "customer": "Customer 2",       "project": "2"    },    {       "customer": "Customer 2",       "project": "3"    } ]We are required to write a JavaScript function that takes one such array, and yields (returns) a new array.In the new array, all the customer keys with same values should be merged and the output should look something like this −const output ... Read More

We are required to write a JavaScript function that takes in an array of strings, (they may be a single character or greater than that). Our function should simply count all the vowels contained in the array.ExampleLet us write the code −const arr = ['Amy','Dolly','Jason','Madison','Patricia']; const countVowels = (arr = []) => {    const legend = 'aeiou';    const isVowel = c => legend.includes(c);    let count = 0;    arr.forEach(el => {       for(let i = 0; i < el.length; i++){          if(isVowel(el[i])){             count++;          };       };    });    return count; }; console.log(countVowels(arr));OutputAnd the output in the console will be −10

Suppose we have an array that contains name of some people like this:const arr = ['Amy', 'Dolly', 'Jason', 'Madison', 'Patricia'];We are required to write a JavaScript function that takes in one such string as the first argument, and two lowercase alphabet characters as second and third argument. Then, our function should filter the array to contain only those elements that start with the alphabets that fall within the range specified by the second and third argument.Therefore, if the second and third argument are 'a' and 'j' respectively, then the output should be −const output = ['Amy', 'Dolly', 'Jason'];ExampleLet us write ... Read More

We have two sets of ranges; one is a single range of any length (R1) and the other is a set of ranges (R2) some or parts of which may or may not lie within the single range (R1).We need to calculate the sum of the ranges in (R2) - whole or partial - that lie within the single range (R1).const R1 = [20, 40]; const R2 = [[14, 22], [24, 27], [31, 35], [38, 56]];Result = 2+3+4+2 = 11R1 = [120, 356]; R2 = [[234, 567]];Result 122ExampleLet us write the code −const R1 = [20, 40]; const R2 = [[14, 22], ... Read More

For this, use Object.keys() along with reduce(). To display the result, we will also use concat().ExampleFollowing is the code −var details = { name: ["John", "David"], age1: "21", age2: "23" },    output = Object       .keys(details)       .reduce((obj, tempKey) =>          (obj[tempKey] = [].concat(details[tempKey]), obj), {}) console.log(output)  To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo302.js.OutputThis will produce the following output on console −PS C:\Users\Amit\javascript-code> node demo302.js { name: [ 'John', 'David' ], age1: [ '21' ], age2: [ '23' ] }

Let’s say we have marks records and we need to sum them. The records are displayed in Radio Button −Marks1 75 {          if (evnt.checked) {             total = total + parseInt(evnt.value);             return;          }       });       secondMark.forEach((evnt) => {          if (evnt.checked) {             total = total + parseInt(evnt.value);             return;          }       });       ... Read More

Let’s say the following is our array −var values = [7,5,3,8,9,'/',9,5,8,2,'/',3,4,8];To merge specific elements, use map along with split().ExampleFollowing is the code −var values = [7,5,3,8,9,'/',9,5,8,2,'/',3,4,8]; var afterMerge = values.join('') .split(/(\d+)/). filter(Boolean). map(v => isNaN(v) ? v : +v); console.log(afterMerge);To run the above program, you need to use the following command −node fileName.js. Here, my file name is demo301.js.OutputThis will produce the following output on console −PS C:\Users\Amit\javascript-code> node demo301.js [ 75389, '/', 9582, '/', 348 ]

For this, you can use ternary operator based on some condition.ExampleFollowing is the code −const yearRangeValue = 18; const getCorrectCentury = dateValues => {    var [date, month, year] = dateValues.split("-");    var originalYear = +year > yearRangeValue ? "20" + year : "18" + year;    return new Date(date + "-" + month + "-" + originalYear).toLocaleDateString('en-GB') }; console.log(getCorrectCentury('10-JAN-19'));To run the above program, you need to use the following command −node fileName.js.Here, my file name is demo300.js.OutputThis will produce the following output on console −PS C:\Users\Amit\javascript-code> node demo300.js 1/10/2019

The get keyword can be used as a getter function like C#, Java and other technologies.We set a function with get like the following in a class −class Employee {    constructor(name) {    this.name = name;    }    get fullName() {       return this.name;    } }ExampleFollowing is the code displaying an example of get −class Employee {    constructor(name) {       this.name = name;    }    get fullName() {       return this.name;    } } var employeeObject = new Employee("David Miller"); console.log(employeeObject.fullName);To run the above program, you need to use ... Read More