Number of Lines To Write String LeetCode solution in JavaScript

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var numberOfLines = function (widths, s) {
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  let pixel = 100,
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    line = 1;
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  for (let i = 0; i < s.length; i++) {
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    if (pixel >= widths[s[i].charCodeAt() - 97]) {
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      pixel -= widths[s[i].charCodeAt() - 97];
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    } else {
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      // this word should be written in NEXT line, so it CANNOT count.
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      i--;
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      line++;
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      pixel = 100;
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    }
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  }
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  // 100-pixel = space used in this line.
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  return [line, 100 - pixel];
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};