JSFiddle - React, Tailwind, and code Playground

HTML

<table>
   <tr>
			<td>
				<label for="analogue_rapides">Analogues rapides<br>
				<select class="input" id="analogue_rapides" name="analogue_rapides" style="width:130px">  
				   <option>choisissez...</option>
				   <option value="apidra">Apidra</option>
				   <option value="novorapid">Novorapid</option>
				   <option value="humalog">Humalog</option>
				   <option value="autre">Autre</option>
				</select></label>
			</td>
			<td>
				<label for="dose_analogue">Dose<br>
				<input type="number" min="1" max="4" step="1" tabindex="10" size="20" value="" class="input" id="dose_analogue" name="dose_analogue"></label><br>
				<label for="injection_analogue">Nombre d'injection/jour<br>
				<input type="number" min="1" max="4" step="1" tabindex="10" size="20" value="" class="input" id="injection_analogue" name="injection_analogue"></label>
			</td>
			<td>
				<label for="doseT_analogue">Dose totale<br>
				<input type="text" tabindex="10" size="20" value="---" class="input" id="doseT_analogue" name="doseT_analogue" disabled="disabled"></label> (UI/j)
			</td>
		</tr>
		<tr>
			<td>
				<label for="analogue_lentes">Analogues lentes<br>
				<select class="input" id="analogue_lentes" name="analogue_lentes" style="width:130px">  
				   <option>choisissez...</option>
				   <option value="lantus">Lantus</option>
				   <option value="levemir">Levemir</option>
				   <option value="insulatard">Insulatard</option>
				   <option value="autre">Autre</option>
				</select></label>
			</td>
			<td>
				<label for="dose_analogueL">Dose<br>
				<input type="number" min="1" max="4" step="1" tabindex="10" size="20" value="" class="input" id="dose_analogueL" name="dose_analogueL"></label><br>
				<label for="injection_analogueL">Nombre d'injection/jour<br>
				<input type="number" min="1" max="4" step="1" tabindex="10" size="20" value="" class="input" id="injection_analogueL" name="injection_analogueL"></label>
			</td>
			<td>
				<label for="doseT_analogueL">Dose...

JavaScript

var e13 = document.getElementById("analogue_rapides");
	var elem_dose_analogue = document.getElementById("dose_analogue");
    var elem_injection_analogue = document.getElementById("injection_analogue");
	
	function calcul_mgj13() {
		
		var list_idx = e13.options[e13.selectedIndex].index;
        
		var nb_mg = document.getElementById("dose_analogue");
		var mg = parseFloat(nb_mg.value);
		
		var elem_dose = document.getElementById("injection_analogue");
		var dose = parseFloat(elem_dose.value);
		
		var elem_result = document.getElementById("doseT_analogue");
		
		if (elem_dose.value != ''){
			elem_result.value = parseFloat(mg * dose).toFixed(2);
		}
		
		e15.disabled=(list_idx > 0);
        elem_dose_analogueM.disabled=(list_idx > 0);
        elem_injection_analogueM.disabled=(list_idx > 0);
		
	}
	elem_dose_analogue.addEventListener("blur", calcul_mgj13);
	elem_injection_analogue.addEventListener("blur", calcul_mgj13);
	


    var e14 = document.getElementById("analogue_lentes");
	var elem_dose_analogueL = document.getElementById("dose_analogueL");
    var elem_injection_analogueL = document.getElementById("injection_analogueL");

	function calcul_mgj14() {
		
		var list_idx = e14.options[e14.selectedIndex].index;
        
		var nb_mg = document.getElementById("dose_analogueL");
        var mg = parseFloat(nb_mg.value);
		
		var elem_dose = document.getElementById("injection_analogueL");
		var dose = parseFloat(elem_dose.value);
		
		var elem_result = document.getElementById("doseT_analogueL");
		
		if (elem_dose.value != ''){
			elem_result.value = parseFloat(mg * dose).toFixed(2);
		}
		
		e15.disabled=(list_idx > 0);
        elem_dose_analogueM.disabled=(list_idx > 0);
        elem_injection_analogueM.disabled=(list_idx > 0);
		
	}
	elem_dose_analogueL.addEventListener("blur", calcul_mgj14);
	elem_injection_analogueL.addEventListener("blur", calcul_mgj14);


    var e15 = document.getElementById("analogueM");
	var elem_dose_analogueM =...