Make IADemoBr work on old browsers

[cdrini]

[codecov[bot]]

Codecov Report

Merging #933 (357f38a) into master (dcc163e) will decrease coverage by 0.00%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #933      +/-   ##
==========================================
- Coverage   69.24%   69.24%   -0.01%     
==========================================
  Files          58       58              
  Lines        5154     5157       +3     
  Branches      846      846              
==========================================
+ Hits         3569     3571       +2     
- Misses       1573     1574       +1     
  Partials       12       12              

Impacted Files	Coverage Δ
src/BookNavigator/book-navigator.js	80.23% <0.00%> (-0.25%)	:arrow_down:

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