Identity matrix construction from the KroneckerDelta function

matrix-identity-from-kronecker.js

'use strict';
// kronecker delta
let kd = (i, j) => i == j ? 1 : 0;

// (In)ij identity matrix constructor
let I = n => {
  let a = [], k = 0;
  for (let i = 0; i < n; ++i)
    for (let j = 0; j < n; ++j)
    a[k++] = kd(i, j);
  return a;
};

// constructs
let mat2 = _ => I(2);
let mat3 = _ => I(3);
let mat4 = _ => I(4);

// proof
console.log(4 == mat2().length);
console.log(9 == mat3().length);
console.log(16 == mat4().length);