JSFiddle - React, Tailwind, and code Playground

HTML

<div class="svg_box">
    <svg
   id="svg_map" viewBox="74 58 617 902" preserveAspectRatio="xMidYMid meet">
  <g
     id="viewport">
    <g
       id="County_fills">
      <g
         id="wicklow">
        <path
           d="m 660.19812,671.17693 c 4.3002,-24.4434 25.98479,-42.3466 13.668,-66.4151 3.521,-20.6076 -8.00616,-48.1039 -28.42028,-38.027 -11.84916,-7.4307 -15.52234,9.0615 -25.5361,-10.1857 -13.21206,-5.8314 -15.00724,18.141 -19.90659,23.682 -3.4252,15.0746 -22.32726,16.7667 -25.17803,34.5218 -0.30454,15.0967 8.81716,24.9106 24.882,22.849 7.57843,8.1943 17.12841,-1.2087 9.03025,18.9026 -10.09526,5.7923 -29.7139,-17.2323 -30.74574,1.6656 7.44289,0.675 23.28352,39.2398 37.71449,22.0728 5.70401,-21.6558 29.89655,-24.6066 41.068,-9.182 -0.82169,2.7052 6.39378,3.4876 3.424,0.116 z"
           id="path3626" />
      </g>
      <g
         id="wexford">
        <path
           d="m 540.52146,777.45573 c -3.04524,-9.6663 13.00966,-37.485 8.31062,-35.5454 3.88412,-7.9903 17.27589,-16.0912 23.13104,-27.5364 -2.13273,-19.9195 22.63382,-22.6222 16.51831,-36.1075 11.01893,-8.0809 29.79595,10.9627 32.60273,-16.1616 11.38006,-10.159 39.99633,3.3896 37.44396,14.9931 -15.37892,21.9284 1.57361,48.5357 -24.976,67.711 4.46987,17.4187 -14.1046,19.387 -18.315,9.989 -4.94644,13.4277 16.44607,15.0034 12.025,19.053 10.52558,3.4549 9.05452,29.7926 -0.184,21.644 1.46896,-8.5511 -8.41153,6.9561 -13.321,-4.809 -3.78015,15.3653 -45.93915,-3.2067 -39.59,-3.884 7.43103,-13.5897 -10.5116,7.1873 -7.215,12.259 -19.22884,17.1015 -15.0041,-7.3152 -26.14055,-21.7183 -9.56407,-3.9302 6.83315,2.1153 -0.29011,0.1131 z"
           id="path3629" />
      </g>
      <g
         id="westmeath">
        <path
           d="m 416.70588,534.86753 c 18.45294,15.2314 34.39666,-12.9194 49.33069,-6.9039 -1.13856,20.7847 21.94788,15.805 35.06155,4.2483 23.30663,-10.3069 46.26826,-21.1292 46.91066,-46.527 12.07974,-8.279 1.11249,-37.0403 -11.57238,-20.7705 -21.3405,-2.5503 -22.76406,-43.2181...

CSS

.svg_box{
    width: 100%;
    height: 100%;
}

#svg_map{
    width: 100%;
    height: 100%;
}

JavaScript

var bbox=document.getElementById("viewport").getBBox();
console.log("bbox=",bbox);