Roman Numeral Converter efficiency

[ajosephs1]

I recently finished the Roman Numeral Converter in the JavaScript Algorithms and Data Structures Projects challenges and I was wondering if this could be simplified. After viewing other peoples solutions I knew my solution was extremely long winded. I could have used other methods but when thinking of early solutions I only thought as far as either using switch statements, else if statements or an object oriented solution.
My solution worked but I noticed even the freecodecamp website took while to run all lines of code.
Please let me know what you think and how I can be more efficient in the future; I’ve posted my solution below. (also this is my first post on the forum, not sure if I formatted it correctly and thanks for feedback in advance!)

function convertToRoman(num) {
  //if num / 1000 >= 1 add m
  //else get remainder and follow if procedures 
  let romanNum = ""
  let remainder = ""
  //if number is > 1000
  if (num / 1000 >= 1) {
    for (let i = 0; i < Math.floor(num / 1000); i++) {
      romanNum += "M"
    }
    remainder = num % 1000
    // determines numeral for 100's position 
    if (remainder / 900 >= 1) {
      romanNum += "CM"
      remainder = remainder % 900
    }
    else if (remainder / 500 >= 1 && remainder / 500 < 2) {
      romanNum += 'D'
      remainder = remainder % 500
      if (remainder / 100 >= 1 && remainder / 100 < 4) {
        for (let i = 0; i < Math.floor(remainder / 100); i++) {
          romanNum += "C"
        }
        remainder = remainder % 100
        console.log(remainder)
      }
    }
    else if (remainder / 400 >= 1 && remainder / 400 < 1.25) {
      romanNum += 'CD'
      remainder = remainder % 400
    }
    else if (remainder / 100 >= 1 && remainder / 100 < 4) {
      for (let i = 0; i < Math.floor(remainder / 100); i++) {
        romanNum += "C"
      }
      remainder = remainder % 100
    }
    // determines numeral for 10 position
    if (remainder / 90 >= 1 && remainder / 90 < 100 / 90) {
      romanNum += "XC"
      remainder = remainder % 90
    }
    else if (remainder / 50 >= 1 && remainder / 50 < 1.8) {
      romanNum += "L"
      remainder = remainder % 50
      if (remainder / 10 >= 1 && remainder / 10 < 4) {
        for (let i = 0; i < Math.floor(remainder / 10); i++) {
          romanNum += "X"
        }
        remainder = remainder % 10
      }
    }
    else if (remainder / 40 >= 1 && remainder / 40 < 1.25) {
      romanNum += "XL"
      remainder = remainder % 40
    }
    else if (remainder / 10 >= 1 && remainder / 10 < 4) {
      for (let i = 0; i < Math.floor(remainder / 10); i++) {
        romanNum += "X"
      }
      remainder = remainder % 10
    }
    //determins numerals for 1's positions 
    if (remainder / 9 >= 1 && remainder / 9 < 10 / 9) {
      romanNum += "IX"
    }
    else if (remainder / 5 >= 1 && remainder / 5 < 1.8) {
      romanNum += "V"
      remainder = remainder % 5
      //determins remainder after 5
      if (remainder / 1 >= 1 && remainder / 1 < 4) {
        for (let i = 0; i < Math.floor(remainder / 1); i++) {
          romanNum += "I"
        }
      }
    }
    else if (remainder / 4 >= 1 && remainder / 4 < 1.25) {
      romanNum += "IV"
    }
    else if (remainder / 1 >= 1 && remainder / 1 < 4) {
      for (let i = 0; i < Math.floor(remainder / 1); i++) {
        romanNum += "I"
      }
    }

  }
  else if (num / 100 >= 1 && num / 100 < 10) {
    remainder = num % 1000
    // determines numeral for 100's position 
    if (remainder / 900 >= 1) {
      romanNum += "CM"
      remainder = remainder % 900
    }
    else if (remainder / 500 >= 1 && remainder / 500 < 2) {
      romanNum += 'D'
      remainder = remainder % 500
      if (remainder / 100 >= 1 && remainder / 100 < 4) {
        for (let i = 0; i < Math.floor(remainder / 100); i++) {
          romanNum += "C"
        }
        remainder = remainder % 100
        console.log(remainder)
      }
    }
    else if (remainder / 400 >= 1 && remainder / 400 < 1.25) {
      romanNum += 'CD'
      remainder = remainder % 400
    }
    else if (remainder / 100 >= 1 && remainder / 100 < 4) {
      for (let i = 0; i < Math.floor(remainder / 100); i++) {
        romanNum += "C"
      }
      remainder = remainder % 100
    }
    // determines numeral for 10 position
    if (remainder / 90 >= 1 && remainder / 90 < 100 / 90) {
      romanNum += "XC"
      remainder = remainder % 90
    }
    else if (remainder / 50 >= 1 && remainder / 50 < 1.8) {
      romanNum += "L"
      remainder = remainder % 50
      if (remainder / 10 >= 1 && remainder / 10 < 4) {
        for (let i = 0; i < Math.floor(remainder / 10); i++) {
          romanNum += "X"
        }
        remainder = remainder % 10
      }
    }
    else if (remainder / 40 >= 1 && remainder / 40 < 1.25) {
      romanNum += "XL"
      remainder = remainder % 40
    }
    else if (remainder / 10 >= 1 && remainder / 10 < 4) {
      for (let i = 0; i < Math.floor(remainder / 10); i++) {
        romanNum += "X"
      }
      remainder = remainder % 10
    }
    //determins numerals for 1's positions 
    if (remainder / 9 >= 1 && remainder / 9 < 10 / 9) {
      romanNum += "IX"
    }
    else if (remainder / 5 >= 1 && remainder / 5 < 1.8) {
      romanNum += "V"
      remainder = remainder % 5
      //determins remainder after 5
      if (remainder / 1 >= 1 && remainder / 1 < 4) {
        for (let i = 0; i < Math.floor(remainder / 1); i++) {
          romanNum += "I"
        }
      }
    }
    else if (remainder / 4 >= 1 && remainder / 4 < 1.25) {
      romanNum += "IV"
    }
    else if (remainder / 1 >= 1 && remainder / 1 < 4) {
      for (let i = 0; i < Math.floor(remainder / 1); i++) {
        romanNum += "I"
      }
    }
  }
  else if (num / 10 >= 1 && num / 10 < 10) {
    remainder = num % 100
    if (remainder / 90 >= 1 && remainder / 90 < 100 / 90) {
      romanNum += "XC"
      remainder = remainder % 90
    }
    else if (remainder / 50 >= 1 && remainder / 50 < 1.8) {
      romanNum += "L"
      remainder = remainder % 50
      if (remainder / 10 >= 1 && remainder / 10 < 4) {
        for (let i = 0; i < Math.floor(remainder / 10); i++) {
          romanNum += "X"
        }
        remainder = remainder % 10
      }
    }
    else if (remainder / 40 >= 1 && remainder / 40 < 1.25) {
      romanNum += "XL"
      remainder = remainder % 40
    }
    else if (remainder / 10 >= 1 && remainder / 10 < 4) {
      for (let i = 0; i < Math.floor(remainder / 10); i++) {
        romanNum += "X"
      }
      remainder = remainder % 10
    }
    //determins numerals for 1's positions 
    if (remainder / 9 >= 1 && remainder / 9 < 10 / 9) {
      romanNum += "IX"
    }
    else if (remainder / 5 >= 1 && remainder / 5 < 1.8) {
      romanNum += "V"
      remainder = remainder % 5
      //determins remainder after 5
      if (remainder / 1 >= 1 && remainder / 1 < 4) {
        for (let i = 0; i < Math.floor(remainder / 1); i++) {
          romanNum += "I"
        }
      }
    }
    else if (remainder / 4 >= 1 && remainder / 4 < 1.25) {
      romanNum += "IV"
    }
    else if (remainder / 1 >= 1 && remainder / 1 < 4) {
      for (let i = 0; i < Math.floor(remainder / 1); i++) {
        romanNum += "I"
      }
    }
  }
  else if (num / 1 >= 1 && num / 1 < 10) {
    remainder = num % 10
    //determins numerals for 1's positions 
    if (remainder / 9 >= 1 && remainder / 9 < 10 / 9) {
      romanNum += "IX"
    }
    else if (remainder / 5 >= 1 && remainder / 5 < 1.8) {
      romanNum += "V"
      remainder = remainder % 5
      //determins remainder after 5
      if (remainder / 1 >= 1 && remainder / 1 < 4) {
        for (let i = 0; i < Math.floor(remainder / 1); i++) {
          romanNum += "I"
        }
      }
    }
    else if (remainder / 4 >= 1 && remainder / 4 < 1.25) {
      romanNum += "IV"
    }
    else if (remainder / 1 >= 1 && remainder / 1 < 4) {
      for (let i = 0; i < Math.floor(remainder / 1); i++) {
        romanNum += "I"
      }
    }
  }
  return romanNum;
}

convertToRoman(36);
console.log(convertToRoman(1700))

[sanity]

Notice that there are parts that are repeated in various parts of code after going into seemingly different if branches. This means while there might be some parts that need some different operations, depending on the if condition, the repeated parts are not it and they could be extracted from the if. To cut both on the code length and complexity.

In a simplified example:

let valueA = 0;
let valueB = 0;
if (value > 5) {
  valueA += 5;
  valueB += 10;
} else {
  valueB += 10;
}

This could be written as:

let valueA = 0;
let valueB = 0;
if (value > 5) {
  valueA += 5;
} 
valueB += 10;