Minimum Jumps to Reach Home LeetCode solution in JavaScript

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var minimumJumps = function (forbidden, a, b, x) {
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  let f = new Set(forbidden);
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  let m = 2000 + 2 * b;
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  let memo = {};
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  let visited = new Set();
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  let res = dfs(0, true);
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  return res === Infinity ? -1 : res;
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  function dfs(i, canJumpBack) {
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    if (i === x) return 0;
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    let key = `${i},${canJumpBack}`;
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    visited.add(i);
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    if (memo[key] !== undefined) return memo[key];
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    if (i > m || i < 0) return Infinity;
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    let min = Infinity;
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    if (canJumpBack && !f.has(i - b) && !visited.has(i - b)) {
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      min = Math.min(min, 1 + dfs(i - b, false));
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    }
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    if (!f.has(i + a) && !visited.has(i + a)) {
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      min = Math.min(min, 1 + dfs(i + a, true));
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    }
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    visited.delete(i);
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    return (memo[key] = min);
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  }
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};