If i have an array A = [1, 4, 3, 2] and B = [0, 2, 1, 2] I want to return a new array (A - B) with values [1, 2, 2, 0]. What is the most efficient approach to do this in javascript?
6 Answers
const A = [1, 4, 3, 2]
const B = [0, 2, 1, 2]
console.log(A.filter(n => !B.includes(n)))Use map method The map method takes three parameters in it's callback function like below
currentValue, index, arrayvar a = [1, 4, 3, 2], b = [0, 2, 1, 2]
var x = a.map(function(item, index) { // In this case item correspond to currentValue of array a, // using index to get value from array b return item - b[index];
})
console.log(x);For Simple and efficient ever.
Check here : JsPref - For Vs Map Vs forEach
var a = [1, 4, 3, 2], b = [0, 2, 1, 2], x = [];
for(var i = 0;i<=b.length-1;i++) x.push(a[i] - b[i]);
console.log(x);If you want to override values in the first table you can simply use forEach method for arrays forEach. ForEach method takes the same parameter as map method (element, index, array). It's similar with the previous answer with map keyword but here we are not returning the value but assign value by own.
var a = [1, 4, 3, 2], b = [0, 2, 1, 2]
a.forEach(function(item, index, arr) { // item - current value in the loop // index - index for this value in the array // arr - reference to analyzed array arr[index] = item - b[index];
})
//in this case we override values in first array
console.log(a);const A = [1, 4, 3, 2]
const B = [0, 2, 1, 2]
const C = A.map((valueA, indexInA) => valueA - B[indexInA])
console.log(C) // [1, 2, 2, 0]Here the map is returning the substraction operation for each number of the first array.
Note: this will not work if the arrays have different lengths
1One-liner using ES6 for the array's of equal size in length:
let subResult = a.map((v, i) => v - b[i]); // [1, 2, 2, 0] v = value, i = index
