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How To – Code Snippets

Learn how to code with simplified code snippets.

How to Add Items to the Start of an Array​

Use unshift() to add one or more items to the start of an array.

const fruitsArray = ["Mango", "Apple"];

fruitsArray.unshift("Orange", "Lemon", "Grape");

console.log(fruitsArray);

// The fruitsArray's invocation above will return:
// ["Orange", "Lemon", "Grape", "Mango", "Apple"]

How to Add Items to the End of an Array​

Use push() to add one or more items to the end of an array.

const fruitsArray = ["Mango", "Apple"];

fruitsArray.push("Orange", "Lemon", "Grape");

console.log(fruitsArray);

// The fruitsArray's invocation above will return:
// ["Mango", "Apple", "Orange", "Lemon", "Grape"]

How to Add Multiple Items to an Array​

Use splice() to add multiple items to an array.

// Define an array:
const colorsArray = ["red", "blue", "green", "white"];

// Add three items to the colorsArray:
colorsArray.splice(1, 0, "purple", "pink", "tan");

// Print colorsArray's content on the console:
console.log(colorsArray);

// The invocation above will return:
// ["red", "purple", "pink", "tan", "blue", "green", "white"]

How to Check If a Number Is an Integer​

Use Number.isInteger() to check if a number is an integer.

Number.isInteger(578);

// The invocation above will return: true

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How to Check If a String Includes a Value​

Use includes() to check if a string includes a value.

"SunDay, Tuesday, and Friday are good Days".includes("day");

// The invocation above will return: true

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How to Check If an Array Includes a Value​

Use includes() to check if an array includes a value.

[1, 3, 5, 7].includes(5);

// The invocation above will return: true

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How to Compute a Property's Name​

Use a square bracket encased expression as the property's name.

let num = 0;
let enSuites = "East";

const doorNo = {
  [enSuites + ++num]: num,
  [enSuites + ++num]: num,
  [enSuites + ++num]: num,
};

console.log(doorNo);

// The invocation above will return:
{East1: 1, East2: 2, East3: 3}

How to Convert a Boolean Value to Number Type​

Use Number() to convert a Boolean value to Number type.

Number(true);

// The invocation above will return: 1

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How to Convert a Date to Number Type​

Use Number() to convert a date to Number type.

Number(new Date(2022, 06, 01));

// The invocation above will return: 1656630000000

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How to Convert a JavaScript Array to JSON​

Use stringify() to convert a JavaScript Array to a JSON text.

// Create a JavaScript array:
const myBio = ["Oluwatobi", "Sofela", "CodeSweetly"];

// Convert myBio array to JSON (text format):
JSON.stringify(myBio);

// The invocation above will return: '["Oluwatobi","Sofela","CodeSweetly"]'

How to Convert a JavaScript Object to JSON​

Use stringify() to convert a JavaScript object to a JSON text.

// Create a JavaScript object:
const myBio = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  company: "CodeSweetly",
};

// Convert myBio object to JSON (text format):
JSON.stringify(myBio);

// The invocation above will return:
// '{"firstName":"Oluwatobi","lastName":"Sofela","company":"CodeSweetly"}'

How to Convert a JSON Text to a JavaScript Array​

Use parse() to convert a JSON text to a JavaScript array.

// Create a JSON text:
const myBio = '["Oluwatobi","Sofela","CodeSweetly"]';

// Convert myBio array to JSON (text format):
JSON.parse(myBio);

// The invocation above will return:
["Oluwatobi", "Sofela", "CodeSweetly"];

How to Convert a JSON Text to a JavaScript Object​

Use parse() to convert a JSON text to a JavaScript object.

// Create a JSON text:
const myBio = '{"firstName":"Oluwatobi","lastName":"Sofela","company":"CodeSweetly"}';

// Convert the myBio JSON text to a JavaScript object:
JSON.parse(myBio);

// The invocation above will return:
{ firstName: "Oluwatobi", lastName: "Sofela", company: "CodeSweetly" };

How to Convert a Number to a String​

Use toString() to convert a number to a string.

(45).toString();

// The invocation above will return: "45"

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How to Convert a String Number to Number Type​

Use Number() to convert a string number to Number type.

Number("578");

// The invocation above will return: 578

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How to Convert a String to an Array​

Use the spread operator (...) within an array to expand the string value into individual array items.

const myName = "Oluwatobi Sofela";

console.log([...myName]);

// The invocation above will return:
// ["O", "l", "u", "w", "a", "t", "o", "b", "i", " ", "S", "o", "f", "e", "l", "a"]

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How to Convert a String to Decimal​

Use parseInt() to convert a string to decimal.

parseInt("1011001", 2);

// The invocation above will return: 89

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How to Convert a String to Lowercase​

Use toLowerCase() to convert a string to lowercase.

"FRIDAY, MY FRIEND, WAS BORN ON FRIDAY".toLowerCase();

// The invocation above will return: "friday, my friend, was born on friday"

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How to Convert a String to Uppercase​

Use toUpperCase() to convert a string to uppercase.

"friday, my friend, was born on friday".toUpperCase();

// The invocation above will return: "FRIDAY, MY FRIEND, WAS BORN ON FRIDAY"

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How to Convert Array to Object​

Use the spread operator (...) within an object to expand the array into individual object properties.

const myNames = ["Oluwatobi", "Sofela"];
const bio = { ...myNames };

console.log(bio);

// The invocation above will return:
{0: "Oluwatobi", 1: "Sofela"}

How to Convert Binary to Decimal​

Use parseInt() to convert a binary string to decimal.

parseInt("1011001", 2);

// The invocation above will return: 89

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How to Convert Hexadecimal to Decimal​

Use parseInt() to convert a hexadecimal string to decimal.

parseInt("4fc", 16);

// The invocation above will return: 1276

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How to Copy Multiple Items from an Array​

Use slice() to copy multiple items from an array.

// Define an array:
const colorsArray = ["red", "blue", "green", "white", "yellow", "pink"];

// Copy four items from colorsArray—starting from the first index position:
colorsArray.slice(1, 4);

// The invocation above will return: ["blue", "green", "white"]

How to Copy Part of a String in JavaScript​

Use slice() to copy part of a string.

// Define a string:
const colorsString = "red, blue, green, white, yellow, pink";

// Duplicate three of colorsString's characters from the first index position:
const duplicatedColors = colorsString.slice(1, 4);

console.log(duplicatedColors);

// The invocation above will return: "ed,"

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How to Delete an Object's Property​

Use the delete operator to delete an object's property.

const bookmark = { year: 2022, month: "December", day: 25 };

delete bookmark.year;

console.log(bookmark);

// The invocation above will return:
{month: "December", day: 25}

How to Determine If Users Have Scrolled a Web Page to the Bottom​

Check if the web page's remaining scrollable height is equal to or less than zero.

window.addEventListener("scroll", checkIfScrolledToPageBottom);

function checkIfScrolledToPageBottom() {
  const htmlElement = document.getElementsByTagName("html")[0];
  const htmlPageHeight = htmlElement.scrollHeight;
  const viewportHeight = htmlElement.clientHeight;
  const lengthScrolled = htmlElement.scrollTop;
  const totalWebpageScrollableHeight = htmlPageHeight - viewportHeight;
  const remainingScrollableHeight =
    totalWebpageScrollableHeight - lengthScrolled;

  if (remainingScrollableHeight <= 0) {
    alert("Scrolled to the bottom!");
  }
}

How to Duplicate an Array's Content into Another Array​

Use the spread operator (...) to copy an array's content into another array.

const myName = ["Sofela", "is", "my"];
const aboutMe = [...myName];

console.log(aboutMe);

// The invocation above will return: ["Sofela", "is", "my"]

How to Duplicate an Object's Properties into Another Object​

Use the spread operator (...) to copy an object's properties into another object.

const myName = { firstName: "Oluwatobi", lastName: "Sofela" };
const bio = { ...myName };

console.log(bio);

// The invocation above will return:
{firstName: "Oluwatobi", lastName: "Sofela"}

How to Find the Central NPX Cache​

Run the following command on your terminal to get the central NPX cache:

>_ Terminal
npm config get cache

How to Get a Webpage's Headings and IDs​

Use forEach() to loop over a NodeList of the webpage's heading elements.

// Get all the webpage's elements with an id attribute:
const elementsWithID = document.querySelectorAll("[id]");

// Invoke a function for each element in the elementsWithID object:
elementsWithID.forEach((element) => {
  if (element.localName === "h2") {
    console.log(element.innerText);
    console.log(`#${element.id}`);
  }
});
Alternate solution
// Get all the webpage's elements with an id attribute:
const elementsWithID = document.querySelectorAll("[id]");

// Get the JavaScript array's forEach method and call it inside the elementsWithID object. Then, pass a function to the forEach() method:

[].forEach.call(elementsWithID, (element) => {
  const text = element.innerText;
  const id = `#${element.id}`;
  if (element.localName === "h2") {
    console.log(text);
    console.log(id);
  }
});
note

[].forEach is equivalent to Array.prototype.forEach.

How to Get First String Index from Array in JavaScript​

Use indexOf() to get the first index position of an array's string.

["Sunday", "Tuesday", "Friday"].indexOf("Tuesday");

// The invocation above will return: 1

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How to Get First String Index from String in JavaScript​

Use indexOf() to get the first index position of a string's text.

"SunDay, Tuesday, and Friday are good Days".indexOf("day");

// The invocation above will return: 12

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How to Get Last String Index from Array in JavaScript​

Use lastIdexOf() to get the last index position of an array's string.

let daysOfTheWeek = [
  "Sunday",
  "Tuesday",
  "Friday",
  "Sunday",
  "Tuesday",
  "Friday",
];

daysOfTheWeek.lastIndexOf("Tuesday");

// The invocation above will return: 4

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How to Get Last String Index from String in JavaScript​

Use lastIdexOf() to get the last index position of an string's text.

"Sunday, Tuesday, Friday, Sunday, Tuesday, Friday".lastIndexOf("Tuesday");

// The invocation above will return: 33

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How to Remove an Array's First Item​

Use shift() to remove an array's first item.

const numbersArray = [1, 2, 3, 4];

numbersArray.shift();

console.log(numbersArray);

// The invocation above will return: [2, 3, 4]

How to Remove an Array's Last Item​

Use pop() to remove an array's last item.

const numbersArray = [1, 2, 3, 4];

numbersArray.pop();

console.log(numbersArray);

// The invocation above will return: [1, 2, 3]

How to Remove Multiple Items from an Array​

Use splice() to remove multiple items from an array.

// Define an array:
const colorsArray = ["red", "blue", "green", "white", "yellow", "pink"];

// Remove four items from colorsArray—starting from the first index position:
colorsArray.splice(1, 4);

// Print colorsArray's content on the console:
console.log(colorsArray);

// The invocation above will return: ["red", "pink"]

How to Remove Whitespace from a String's End part​

Use trimEnd() to remove whitespace from a string's end part.

const myColor = "          I love blue.          ";

// Remove whitespace characters from the end part of myColor:
myColor.trimEnd();

// The invocation above will return: "          I love blue."

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How to Remove Whitespace from Both Ends of a String​

Use trim() to remove whitespace from both ends of a string.

const myColor = "          I love blue.          ";

// Remove whitespace characters from both ends of myColor:
myColor.trim();

// The invocation above will return: "I love blue."

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How to Remove Whitespace from the Start of a String​

Use trimStart() to remove whitespace from the beginning of a string.

const myColor = "          I love blue.          ";

// Remove whitespace characters at the beginning of myColor:
myColor.trimStart();

// The invocation above will return: "I love blue.          "

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How to Replace Part of a Text String​

Use replace() to replace parts of a text.

"Friday, my friend, was born on Friday.".replace("Friday", "Sunday");

// The invocation above will return: "Sunday, my friend, was born on Friday."

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How to Search a String in JavaScript​

Use search() to search a JavaScript string.

"SunDay, Tuesday, and Friday are good DAYS".search(/day/);

// The invocation above will return: 12

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How to Split a String in JavaScript​

Use split() to split a JavaScript string.

"On the day".split("");

// The invocation above will return:
// ["O", "n", " ", "t", "h", "e", " ", "d", "a", "y"]

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How to Swap Two or More Variables' Values​

Option 1: Use object destructuring​

Use object destructuring to swap the values of two or more different variables.

// Define two variables:
let firstName = "Oluwatobi";
let website = "CodeSweetly";

// Reassign the firstName variable with the firstName property's value.
// And reassign the website variable with the website property's content:
({ firstName, website } = { firstName: website, website: firstName });

console.log(firstName); // "CodeSweetly"
console.log(website); // "Oluwatobi"

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Option 2: Use array destructuring​

Use array destructuring to swap the values of two or more different variables.

// Define two variables:
let firstName = "Oluwatobi";
let website = "CodeSweetly";

// Reassign the firstName variable with the array's first item.
// And reassign the website variable with the array's second item:
[firstName, website] = [website, firstName];

console.log(firstName); // "CodeSweetly"
console.log(website); // "Oluwatobi"

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How to test if a string contains a RegExp in JavaScript​

Use test() to test if a string contains a regular expression.

/Color/i.test("My best color is blue.");

// The invocation above will return: true

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How to Use an Array as a Function's Argument​

Use the spread operator (...) to spread the array across the function's parameters.

const numbers = [1, 3, 5, 7];

function addNumbers(a, b, c, d) {
  return a + b + c + d;
}

console.log(addNumbers(...numbers));

// The invocation above will return: 16

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How to Use JSON.stringify() with an Object without Deleting the Object's Function​

Convert the object into a string before invoking JSON.stringify().

// Create a JavaScript object:
const myBio = {
  firstName: "Oluwatobi",
  lastName: function () {
    return "Sofela";
  },
  company: "CodeSweetly",
};

// Convert the lastName function to a string:
myBio.lastName = myBio.lastName.toString();

// Convert myBio object to JSON (text format):
JSON.stringify(myBio);

// The invocation above will return:
// '{"firstName":"Oluwatobi","lastName":"function () {\\n    return \\"Sofela\\";\\n  }","company":"CodeSweetly"}'