How to subtract one array from another, element-wise, in javascript

Question

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 e

Answer 1

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);

Answer 2

const A = [1, 4, 3, 2]
const B = [0, 2, 1, 2]
console.log(A.filter(n => !B.includes(n)))

Answer 3

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);

Answer 4

Use map method The map method takes three parameters in it's callback function like below

currentValue, index, array

var 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);