taxCalculator.js

const tax = [[0, 0.1],
           [1000, 0.2],
           [4000, 0.3],   
           [6000, 0.4],
            [6700, 0.6]];

const calcTax = (taxesTable, income) => {
  let total = 0;

  let index = taxesTable.findIndex((item) => {
    return item[0] > income;
  });
  
  if(index === -1) {
    index = taxesTable.length;
  }
 
  
  console.log(index);
    
  for(let i = 0; i < index; i++) {
    if(index === 1) {
      total = (income * taxesTable[i][1]);
      console.log(total)
    } else if(i + 1 === index){
      console.log((income - taxesTable[i][0]) * taxesTable[i][1])
      total += (income - taxesTable[i][0]) * taxesTable[i][1];
    } else {
      console.log((taxesTable[i + 1][0] - taxesTable[i][0]) * taxesTable[i][1]);
      total += (taxesTable[i + 1][0] - taxesTable[i][0]) * taxesTable[i][1];
    } 
  }
  
  console.log(total);
  console.log('-'.repeat(100));
  
}