Convert a Number to Hexadecimal LeetCode solution in JavaScript

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var toHex = function (num) {
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  let hexSymbols = [
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    "0",
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    "1",
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    "2",
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    "3",
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    "4",
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    "5",
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    "6",
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    "7",
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    "8",
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    "9",
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    "a",
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    "b",
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    "c",
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    "d",
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    "e",
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    "f",
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  ];
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  if (num >= 0) {
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    let hex = "";
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    do {
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      let reminder = num % 16;
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      num = Math.floor(num / 16);
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      hex = hexSymbols[reminder] + hex;
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    } while (num > 0);
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    return hex;
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  } else {
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    num = -num;
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    let invertedHex = ""; //FFFFFFFF - hex
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    let needToCarry1 = true; //adding + 1 initially and carrying it on if needed
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    while (num > 0) {
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      let reminder = num % 16;
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      let invertedReminder = 15 - reminder; //inverting
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      if (needToCarry1) {
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        //adding 1 for 2's complement
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        invertedReminder += 1;
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        if (invertedReminder === 16) {
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          //overflow, carrying 1 to the left
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          invertedReminder = 0;
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          needToCarry1 = true;
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        } else {
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          needToCarry1 = false;
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        }
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      }
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      num = Math.floor(num / 16);
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      invertedHex = hexSymbols[invertedReminder] + invertedHex;
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    }
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    //formatting as "FFFFFFFF"
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    while (invertedHex.length < 8) {
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      invertedHex = "f" + invertedHex;
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    }
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    return invertedHex;
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  }
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};