Number of Ways to Stay in the Same Place After Some Steps LeetCode solution in JavaScript

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var numWays = function (steps, arrLen) {
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  let memo = Array(steps + 1)
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      .fill(0)
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      .map(() => Array(steps + 1).fill(-1)),
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    mod = 10 ** 9 + 7;
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  return dp(0, steps);
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  function dp(i, steps) {
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    if (steps === 0) return i === 0 ? 1 : 0; // found a way
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    if (i > steps || i < 0 || i >= arrLen) return 0; // out of bounds
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    if (memo[i][steps] !== -1) return memo[i][steps]; // memoized
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    let moveLeft = dp(i - 1, steps - 1);
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    let moveRight = dp(i + 1, steps - 1);
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    let stay = dp(i, steps - 1);
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    return (memo[i][steps] = (moveLeft + moveRight + stay) % mod);
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  }
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};