Max Points on a Line LeetCode solution in JavaScript

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/**
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 * @param {number[][]} points
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 * @return {number}
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 */
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var maxPoints = function (points) {
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  if (points.length === 1) {
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    return 1;
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  }
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  const slopes = {};
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  let dx, dy;
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  let xbase, ybase;
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  let xref, yref, key;
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  const INFINITE_SLOPE = "infinite";
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  for (let i = 0; i < points.length; i++) {
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    [xbase, ybase] = points[i];
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    for (let j = i + 1; j < points.length; j++) {
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      [xref, yref] = points[j];
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      if (xref === xbase) {
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        key = `x = ${xref}`;
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      } else {
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        dx = xref - xbase;
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        dy = yref - ybase;
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        let m = dy / dx;
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        let c = yref - m * xref;
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        m = m.toFixed(4);
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        c = c.toFixed(4);
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        key = `y = ${m}x + ${c}`;
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      }
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      slopes[key] || (slopes[key] = 0);
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      slopes[key]++;
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    }
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  }
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  const maxPairs = Math.max(...Object.values(slopes));
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  if (maxPairs === 2) {
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    return 2;
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  }
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  for (let i = 1; i <= 300; i++) {
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    if ((i * (i - 1)) / 2 === maxPairs) {
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      return i;
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    }
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  }
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  return 0;
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};