JSFiddle - React, Tailwind, and code Playground

JavaScript

var X= [10, 25, 30, 40]; Y=[5, 4, 7, 12];
 
 var Slope, Intercept, SX = 0, SY = 0,
            SXX = 0, SXY = 0, SYY = 0,
            SumProduct = 0, N = X.length;

            for (var i = 0; i < N; i++) {
                SX = SX + X[i];
                SY = SY + Y[i];
                SXY = SXY + X[i] * Y[i];
                SXX = SXX + X[i] * X[i];
                SYY = SYY + Y[i] * Y[i];
            }
            
            Slope = ((N * SXY) - (SX * SY)) / ((N * SXX) - (SX * SX));
            
            Intercept = (SY - (Slope * SX)) / N;
            
            alert("Slope: " + Slope + ", Intercept: " + Intercept );