Arrays
Union of arrays
let a = [1, 2, 3, 4, 5];
let b = [3, 4, 5, 6, 7];
let result = [...new Set([...a, ...b])]; // [1, 2, 3, 4, 5, 6, 7]
Intersection of arrays
let a = [1, 2, 3, 4, 5];
let b = [2, 3, 4, 6];
let result = a.filter(val => ~b.indexOf(val)); // [2, 3, 4]
Get non intersected values
let a = [1, 2, 3, 4, 5];
let b = [2, 3, 4, 6];
let result = a.filter(val => !~b.indexOf(val)); // [1, 5]
Printing array of array values in a new line
const a = [
[11],
[7, 15],
[5, 9, 13, 20],
[3, 6, 8, 10, 12, 14, 18, 25]
];
const result = a.reduce((el, acc) => el + acc.join(' ') + '\n', '\n');
// output
/*
11
7 15
5 9 13 20
3 6 8 10 12 14 18 25
*/
Removing duplicates from an array
/*
#method 1
*/
let fruits = ['banana','mango','apple','sugarcane','mango','apple']
let uniqueFruits = Array.from(new Set(fruits));
// uniqueFruits -- [ 'banana', 'manago', 'apple', 'sugarcane' ]
/*
# method 2
*/
let uniqueFruits2 = [...new Set(fruits)];
// uniqueFruits2 -- [ 'banana', 'manago', 'apple', 'sugarcane' ]
Replace the specific value in an array
var fruits2 = [...fruits];
fruits2.splice(0,2,"potato","tomato");
// fruits2 ['potato', 'tomato', 'apple', 'sugarcane', 'manago', 'apple' ]
Mapping array without maps
let friends = [
{name:"John", age:22},
{name:"Peter", age:23},
{name:"bimbo",age:34},
{name:"mark",age:45},
{name:"Esther",age:21},
{name:"Monica",age:19}
];
let friendNames = Array.from(friends,({name})=>name);
// friendNames -- ['John', 'Peter', 'bimbo', 'mark', 'Esther', 'Monica' ]
Emptying an array
let fruits = ['banana','mango','apple','sugarcane','mango','apple']
fruits.length = 0;
// fruits -- []
Convert an array to an object
let fruits = ['banana','manago','apple','sugarcane','manago','apple']
const fruitsObj = {...fruits};
// fruitsObj -- {'0': 'banana','1': 'mango', '2': 'apple','3': 'sugarcane','4': 'mango','5': 'apple'}
### Fulfill array with data
let newArray = new Array(10).fill("1");
// newArray -- ['1', '1', '1', '1','1', '1', '1', '1','1', '1']
Merging Arrays
let fruits = ['banana','manago','apple'];
let meat = ["Poultry","beef","fish"]
let vegetables = ["Potato","tomato","cucumber"];
let food = [...fruits,...meat,...vegetables];
// food -- ['banana', 'manago','apple', 'sugarcane','manago', 'apple','Poultry', 'beef','fish', 'Potato','tomato', 'cucumber']
Merging only duplicates value in two arrays
let numOne = [0,2,4,6,8,8];
let numTwo = [1,2,3,4,5,6];
const duplicatedValue = [...new Set(numOne)].filter(item=>numTwo.includes(item));
// duplicatedValue -- [ 2, 4, 6 ]
Remove falsy value from an array.
const mixedArray = [0,"blue","",NaN,true,undefined,"white",false];
const filteredArray = mixedArray.filter(Boolean);
// filteredArray -- [ 'blue', true, 'white' ]
Reverse an array
const colors = ['blue','red','green','black'];
const reverseColors = colors.reverse();
// reverseColors -- [ 'black', 'green', 'red', 'blue' ]
Sum of the value in an array
const val = [1,4,5,7];
const valSum = val.reduce((x,y)=>x+y);
// valSum -- 17
Generate an array from a function Arguments
function f() {
return Array.from(arguments);
}
f(1,2,4))
// result -- [1,2,4]
Strings
Reverse a string
let str = str.split('').reverse().join('');
Replace a character at a particular index
function replaceAt(str, i, char) {
return s.substring(0, i) + char + str.substring(i + 1);
}
Remove last character in a string
javascript
// using substring
str.substring(0, str.length - 1);
// using slice
str.slice(0, -1)
Top comments (0)