JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://code.highcharts.com/highcharts.js"></script>

<div id="container"></div>
<input id="input" value=65 />
<button id="button" type="button">Get X VALUE</button>

JavaScript

$(function () {
    lineWidth = 1,
    lineColor = 'red';
        
   var ttt=$('#container').highcharts({
		plotOptions: {
            series: {
                allowPointSelect: false,
                marker: {
                    states: {
                        select: {
                            enabled: true,
                            fillColor: 'red',
                            color: 'red'
                        }
                    },
                }
                }
            
        },    
		
        title: {
            text: 'Logarithmic axis demo'
        },

		  yAxis: {
            title: {
                text: 'H (Hauteur Man. totale)'
            }
		}	,
			 xAxis: {
            title: {
                text: 'Q<br>Debit'
            }
		}	,
        tooltip: {
            headerFormat: '',
            pointFormat: 'Q = {point.x} m³/h<br>H = {point.y}',
			crosshairs: [true,true]
        },

        series: [{
         type: 'spline',
		name : '',
           
            data: [[1.50,66.00], [1.80,64.00], [2.10,62.00], [2.40,58.00], [2.70,56.00], [3.00,52.00], [3.60,43.00], [4.20,28.00]],
       lineWidth: 4,
		enabledCrosshairs: true,

               
                marker : {
                    enabled : true,
                    radius : 2
                },
                tooltip: {
                    valueDecimals: 2
                }
		
		 }]
    });
    
    //BUTTON CLICK
    $('#button').click(function(){
    y1=$('#input').val();
	
    var points = $('#container').highcharts().series[0].points;
    for (var i = 0; i < points.length; i++) {
        //alert(points[i].y);
        if (points[i].y == y1){
        xValue = points[i].x;
         alert(xValue);
         break;   
        }
    }
       
	//x=ttt.xAxis[0].toPixels(xValue);
    });

});