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W3Resource JavaScript array - Exercises, Practice, Solution
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// 1. Write a JavaScript function to check whether an `input` is an array or not. Go to the editor | |
// Test Data : | |
// console.log(is_array('w3resource')); | |
// console.log(is_array([1, 2, 4, 0])); | |
// false | |
// true | |
// Solution | |
(function () { | |
const isArray = (arr) => { | |
return toString.call(arr) === "[object Array]"; | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 2. Write a JavaScript function to clone an array. Go to the editor | |
// Test Data : | |
// console.log(array_Clone([1, 2, 4, 0])); | |
// console.log(array_Clone([1, 2, [4, 0]])); | |
// [1, 2, 4, 0] | |
// [1, 2, [4, 0]] | |
// Solution | |
(function () { | |
const testArray = [1, 2, [4, 0]]; | |
const cloneArr = (arr) => { | |
return arr.map((item) => { | |
if (Array.isArray(item)) { | |
return cloneArr(item); | |
} else { | |
return item; | |
} | |
}); | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 3. Write a JavaScript function to get the first element of an array. Passing a parameter 'n' will return the first 'n' elements of the array. Go to the editor | |
// Test Data : | |
// console.log(first([7, 9, 0, -2])); | |
// console.log(first([],3)); | |
// console.log(first([7, 9, 0, -2],3)); | |
// console.log(first([7, 9, 0, -2],6)); | |
// console.log(first([7, 9, 0, -2],-3)); | |
// Expected Output : | |
// 7 | |
// [] | |
// [7, 9, 0] | |
// [7, 9, 0, -2] | |
// [] | |
// Solution | |
(function () { | |
const getElements = (arr, n) => { | |
return arr.filter((item, index) => index < n); | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 4. Write a JavaScript function to get the last element of an array. Passing a parameter 'n' will return the last 'n' elements of the array. Go to the editor | |
// Test Data : | |
// console.log(last([7, 9, 0, -2])); | |
// console.log(last([7, 9, 0, -2],3)); | |
// console.log(last([7, 9, 0, -2],6)); | |
// Expected Output : | |
// -2 | |
// [9, 0, -2] | |
// [7, 9, 0, -2] | |
// Solution | |
(function () { | |
const getElements = (arr, n) => { | |
arr.filter((item, index) => index > arr.length - 1 - n); | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 5. Write a simple JavaScript program to join all elements of the following array into a string. Go to the editor | |
// Sample array : myColor = ["Red", "Green", "White", "Black"]; | |
// Expected Output : | |
// "Red,Green,White,Black" | |
// "Red,Green,White,Black" | |
// "Red+Green+White+Black" | |
// Solution | |
(() => { | |
let myColorList = ["Red", "Green", "White", "Black"]; | |
const arrayToString = (arr) => { | |
return arr.toString(); | |
}; | |
arrayToString(myColorList); | |
})(); | |
/****************************************************************************************************************************/ | |
// 6. Write a JavaScript program which accept a number as input and insert dashes (-) between each two even numbers. For example if you accept 025468 the output should be 0-254-6-8 | |
// Solution | |
(() => { | |
let num = 025468; | |
const dashedEvenNumbers = (num) => { | |
numArray = []; | |
num | |
.toString() | |
.match(/\d/gi) | |
.map((item, i) => { | |
const numItem = parseInt(item); | |
// If Item is even and the last item of numArray is also even, first push "-" then number | |
if (numItem % 2 === 0 && numArray[numArray.length - 1] % 2 === 0) { | |
numArray.push("-"); | |
} | |
numArray.push(numItem); | |
}); | |
return numArray.join(""); | |
}; | |
dashedEvenNumbers(num); | |
})(); | |
/****************************************************************************************************************************/ | |
// 7. Write a JavaScript program to find the most frequent item of an array. Go to the editor | |
// Sample array : var arr1=[3, 'a', 'a', 'a', 2, 3, 'a', 3, 'a', 2, 4, 9, 3]; | |
// Solution | |
(() => { | |
var arr = [3, "a", "a", "a", 2, 3, "a", 3, "a", 2, 4, 9, 3]; | |
const getMaxCount = (arr) => { | |
const itemCounter = {}; | |
let maxCount = null; //Saves the item with maxCount | |
// Loop and save the counts in an Object itemCounter | |
arr.map((item) => { | |
if (maxCount === null) { | |
maxCount = item; | |
} | |
if (itemCounter[item]) { | |
itemCounter[item] += 1; | |
} else { | |
itemCounter[item] = 1; | |
} | |
// if the maxCount item has count less than current item's count, update maxCount | |
if (itemCounter[maxCount] < itemCounter[item]) { | |
maxCount = item; | |
} | |
}); | |
return maxCount; | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 8. Write a JavaScript program which accept a string as input and swap the case of each character. For example if you input 'The Quick Brown Fox' the output should be 'tHE qUICK bROWN fOX'. | |
// Solution | |
(() => { | |
const str = "The Quick Brown Fox"; | |
const toggleCase = (str) => { | |
// Get The String Array | |
let strArray = str.match(/\w|(\s\w)/gi); | |
// check if the chars lie in the charCode range above 96 which means they are lowercase | |
strArray = strArray.map((item, i) => { | |
if (item && item.charCodeAt(0) > 96) { | |
return item.toUpperCase(); | |
} else if (item) { | |
return item.toLowerCase(); | |
} else { | |
return item; | |
} | |
}); | |
strArray.join(""); | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
//9. Write a JavaScript program to remove duplicate items from an array (ignore case sensitivity) | |
// Solution | |
(() => { | |
var arr = [1, 1, 2, 3, 4, 1, 2, 5, 7, 8, 0]; | |
const makeItUnique = (arr) => { | |
// Using Sets | |
let setFromArray = new Set(arr); | |
console.log(Array.from(setFromArray)); | |
//alt approach from Object | |
const objFromArray = {}; | |
for (const i of arr) { | |
if (objFromArray[i] === undefined) { | |
objFromArray[i] = true; | |
} | |
} | |
return Object.keys(objFromArray).map((item) => parseInt(item)); | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
//10. Write a JavaScript function to get a random item from an array. | |
// Solution | |
(() => { | |
var arr = [1, 2, 3, 4, 5, 7, 8, 9]; | |
const getARandomItem = (arr) => { | |
return arr[Math.floor(Math.random() * (arr.length - 1))]; | |
}; | |
})(); | |
/****************************************************************************************************************************/ | |
// 11. Write a JavaScript function to create a specified number of elements with pre-filled numeric value array. Go to the editor | |
// Test Data : | |
// console.log(array_filled(6, 0)); | |
// [0, 0, 0, 0, 0, 0] | |
// console.log(array_filled(4, 11)); | |
// [11, 11, 11, 11] | |
// Solution | |
(() => { | |
function renderArray(length, entry) { | |
const arr = new Array(length); | |
return arr.fill(entry); | |
} | |
})(); |
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