Baseball Game LeetCode solution in JavaScript

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//Plus sign in the below algo confirms that the data type we are getting is integer. So, instead of adding it as a string, the data type will be  added as integer
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var calPoints = function (ops) {
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  let stack = [];
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  for (let i = 0; i < ops.length; i++) {
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    if (ops[i] === "C") stack.pop();
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    else if (ops[i] === "D") stack.push(+stack[stack.length - 1] * 2);
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    //we have to take stack.length to get the element of stack. We cannot take i for getting the element of stack as i refers to ops and it wont give the index of previous element in stack
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    else if (ops[i] === "+")
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      stack.push(+stack[stack.length - 1] + +stack[stack.length - 2]);
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    else stack.push(+ops[i]);
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  }
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  let sum = 0;
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  for (let i = 0; i < stack.length; i++) {
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    sum = sum + stack[i];
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  }
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  return sum;
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};