JSFiddle - React, Tailwind, and code Playground

HTML

<div style="width:100%;">
    <img id="img_ID" src="http://credicim.graphicom.tm.fr/images/credicim/map/CARTE-FRANCE-fond-gris-plus-large.png" usemap="#m_CARTEFRANCEfondgrispluslarge" border="0" width="100%" alt="" />
</div>

<map id="map_ID" name="m_CARTEFRANCEfondgrispluslarge">
<area shape="poly" coords="404,351,404,356,402,361,409,361,416,363,420,361,431,362,437,357,433,353,429,354,428,342,433,338,434,330,431,325,425,306,427,303,425,298,418,292,415,286,412,283,413,281,410,277,404,274,398,275,391,273,383,267,379,272,372,273,373,279,368,282,362,279,361,268,357,270,355,276,358,286,353,288,342,285,341,281,331,280,326,275,324,268,320,270,317,274,317,278,313,280,312,281,311,282,309,283,309,285,308,287,309,289,310,292,312,294,315,298,318,301,319,303,321,305,320,306,321,308,322,309,323,309,324,309,326,314,328,317,329,320,330,323,330,327,331,332,332,334,335,338,336,338,335,338,333,334,334,334,335,335,335,336,337,339,341,342,343,343,344,343,346,343,347,344,347,345,346,344,346,344,344,344,344,344,343,344,343,345,345,345,345,346,348,346,350,347,354,348,358,350,358,353,359,355,363,356,366,355,370,357,371,361,372,362,373,362,373,361,373,361,372,359,372,358,374,360,376,364,377,364,378,366,379,366,378,364,377,362,377,362,378,362,379,361,382,359,383,360,386,361,387,360,388,360,389,360,395,357,404,351" href="contacts/vos-conseillers-en-vendee-85.html" title="Vendée (85)" alt="Vendée (85)" >
<area shape="poly"...

JavaScript

window.onload = function () {
    var ImageMap = function (map, img) {
            var n,
                areas = map.getElementsByTagName('area'),
                len = areas.length,
                coords = [],
                previousWidth = 904;
            for (n = 0; n < len; n++) {
                coords[n] = areas[n].coords.split(',');
            }
            this.resize = function () {
                var n, m, clen,
                    x = img.offsetWidth / previousWidth;
                for (n = 0; n < len; n++) {
                    clen = coords[n].length;
                    for (m = 0; m < clen; m++) {
                        coords[n][m] = Math.round(parseInt(coords[n][m], 10) * x);
                    }
                    areas[n].coords = coords[n].join(',');
                }
                previousWidth = document.body.clientWidth;
                return true;
            };
            window.onresize = this.resize;
        },
        imageMap = new ImageMap(document.getElementById('map_ID'), document.getElementById('img_ID'));
    imageMap.resize();
    return;
}