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9 Simple logical questions for JavaScript beginner's

318097 profile image Mehul Lakhanpal ・2 min read

1. Pick a random element from an array

const themes = ['neo', 'black & white', 'color'];

const randomNumber =  Math.round(Math.random() * 100); // random number between 0 - 100
const randomElement = randomNumber % themes.length; // so that the number is within the arrays range 
console.log(themes[randomElement]);
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2. Find sum using reduce()

const arr = [1, 2, 3, 4, 5];

const sum = arr.reduce((previousSum, element) => {
  const newSum = previousSum + element;
  return newSum;
}, 0); // Initially the sum is set to 0

console.log(sum); // 15
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3. Capitalize the first letter of every word

const str = "code drops";

const capitalize = (input) =>
  input
    .split(" ") // split by spaces
    .map((word) => word[0].toUpperCase() + word.slice(1)) // uppercase first character of every word
    .join(" "); // join them back by spaces

capitalize(str); // Code Drops
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4. Insert something in the middle of an array

const arr = [1, 2, 3, 4];
const index = 2;
const insertText = "hello";

// Solution 1 - Split at the index and rejoin them
const result = [...arr.slice(0, index), insertText, ...arr.slice(index)];
console.log(result); // [1, 2, 'hello', 3, 4]

// Solution 2 - .splice() - It can be used to add/remove elements from array
const arrCopy = [...arr]; // splice modified the array on which the operation is performed.
arrCopy.splice(index, 0, insertText); // arguments are - index, no of elements to remove, new element to add
console.log(arrCopy); // [ 1, 2, 'hello', 3, 4 ]
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5. Array.filter()

const numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const numbersGreaterThanFive = numbers.filter(number => number > 5);
console.log(numbersGreaterThanFive); // [6, 7, 8, 9, 10]
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6. Convert array to object using .reduce()

const list = [
  { label: "javascript", color: "blue" },
  { label: "html", color: "red" },
  { label: "css", color: "green" },
];

const initialValue = {};
const convertToObject = (result, item) => {
  const language = item.label;
  const color = item.color;

  return {
    ...result,
    [language]: color,
  };
};

const palette = list.reduce(convertToObject, initialValue);

console.log(palette); // { javascript: 'blue', html: 'red', css: 'green' }
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7. Check if a String is a Palindrome

const isPalindrome = (str) => str === str.split("").reverse().join("");

isPalindrome("codedrops"); // false
isPalindrome("racecar"); // true
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8. Reverse a string

const reverse = str => str.split("").reverse().join("");
reverse('Codedrops.tech'); // hcet.spordedoC
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9. Array.every()

Check if all the elements in the array are greater than 0 using .every()

const arr = [1, 2, -1, 4, -5];

const allGreaterThanZero = arr.every(number => number > 0);
console.log(allGreaterThanZero); // false
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Thanks for reading 💙

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Discussion (2)

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Andrei Dascalu

Honestly I couldn't get over capitilize. And capilatize. They are definitely the awesomest words ever, save for "awesomest"

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