Javascipt to count increment price for each tier

I am new to coding and currently touch the javascript part. I am facing a question about how to calculate the different tier prices and charges as shown in the image: Tier Pricing Table

This is the code that I have tried. i represents the LOAN AMOUNT tier. When i is equal to 1 it will use the next tier percentage to count and the i will +1 ag, but I am not sure is it correct or not… And should I add a EventListener to determine which tier the input now is? Sorry for my broken English. Thanks a lot! ^_^

if(loan >= 500000 && loan < 1000000 && i==0) charge = 1% i = 1

if(loan >= 500000 && loan < 1000000 && i==1) charge = 0.8% i = 2

if(loan >= 2000000 && loan < 2000000 && i==2) charge = 0.7% i = 3

if(loan >= 2000000 && loan < 2000000 && i==3) charge = 0.6% i= 4

Answer

Not quite sure what your goal is, but if you want a system like tax brackets, where the loan amount is charged in portions based on the remaining money and where it fits in a tier it might look a little like this:

const getChargedSums = (amount) => {
  let loanAmount = amount;
  let sums = [];
  
  loanAmount -= 500000; 
    if (loanAmount < 0) {
    sums.push((loanAmount + 500000) * 0.1)
    return sums
  }
  sums.push(500000 * 0.1)

  loanAmount -= 500000; 
  if (loanAmount < 0) {
    sums.push((loanAmount + 500000) * 0.08)
    return sums
  }
  sums.push(500000 * 0.08)
   
  loanAmount -= 2000000; 
  if (loanAmount < 0) {
    sums.push((loanAmount + 2000000) * 0.07)
    return sums
  }
  sums.push(2000000 * 0.07)

  loanAmount -= 2000000;
  if (loanAmount < 0) {
    sums.push((loanAmount + 2000000) * 0.06)
    return sums
  }
  sums.push(2000000 * 0.06)

  loanAmount -= 25000000; 
  if (loanAmount < 0) {
    sums.push((loanAmount + 25000000) * 0.05)
    return sums
  }
  sums.push(25000000 * 0.05)

  sums.push(loanAmount * 0.05)
  return sums
}
let chargedSums = getChargedSums(800000)
console.log('Charged:', chargedSums.reduce((a, b) => a + b, 0))