fix var to const

[QingLianLiu]

Fix var into const

[codecov-io]

Codecov Report

Merging #723 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #723   +/-   ##
=======================================
  Coverage   86.71%   86.71%           
=======================================
  Files          16       16           
  Lines        1746     1746           
=======================================
  Hits         1514     1514           
  Misses        232      232

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[jatinkumarg]

Great work, you can also add 'use strict' at the top of the page.

[PriyankaCodes99]

Looks good. As stated, 'use strict' can be added for strict mode.

[humphd]

This looks really good. I also agree with both your reviewers that you need to add 'use strict; to the top of the file. Please do that, then git add, git commit, and git push again to this same branch. It will get added. Let me know when that's done and I'll re-review.

[humphd]

@QingLianLiu how is this coming?