From edb87507f236c377e3f6927d81c1f81847f0c966 Mon Sep 17 00:00:00 2001
From: Itamar Davidyan <91004029+itamar-owlytics@users.noreply.github.com>
Date: Wed, 29 Dec 2021 11:23:14 +0200
Subject: [PATCH] Use class syntax and extends keyword instead of util.inherits
 (#16)

`util.inherits` is now deprecated due to issues with how it sets
the prototype chain, see:  https://github.com/nodejs/node/issues/4179
---
 hypothesis/one-data-set.js | 18 ++++++++++--------
 hypothesis/two-data-set.js | 25 ++++++++++++++-----------
 hypothesis/welch.js        | 30 ++++++++++++++++--------------
 3 files changed, 40 insertions(+), 33 deletions(-)

diff --git a/hypothesis/one-data-set.js b/hypothesis/one-data-set.js
index 9e3c165..2d55708 100644
--- a/hypothesis/one-data-set.js
+++ b/hypothesis/one-data-set.js
@@ -2,17 +2,19 @@
 
 const Distribution = require('distributions').Studentt;
 
-const util = require('util');
 const AbstactStudentT = require('./abstact.js');
 
-function StudentT(data, options) {
-  AbstactStudentT.call(this, options);
+class StudentT extends AbstactStudentT {
 
-  this._df = data.size - 1;
-  this._dist = new Distribution(this._df);
+  constructor(data, options) {
+    super(options);
+    this._df = data.size - 1;
+    this._dist = new Distribution(this._df);
+  
+    this._se = Math.sqrt(data.variance / data.size);
+    this._mean = data.mean;
+  }
 
-  this._se = Math.sqrt(data.variance / data.size);
-  this._mean = data.mean;
 }
-util.inherits(StudentT, AbstactStudentT);
+
 module.exports = StudentT;
diff --git a/hypothesis/two-data-set.js b/hypothesis/two-data-set.js
index 728db34..b228a2c 100644
--- a/hypothesis/two-data-set.js
+++ b/hypothesis/two-data-set.js
@@ -2,21 +2,24 @@
 
 const Distribution = require('distributions').Studentt;
 
-const util = require('util');
 const AbstactStudentT = require('./abstact.js');
 
-function StudentT(left, right, options) {
-  AbstactStudentT.call(this, options);
+class StudentT extends AbstactStudentT {
+  
+  constructor(left, right, options) {
+    super(options);
 
-  this._df = left.size + right.size - 2;
-  this._dist = new Distribution(this._df);
+    this._df = left.size + right.size - 2;
+    this._dist = new Distribution(this._df);
 
-  const commonVariance = ((left.size - 1) * left.variance +
-                          (right.size - 1) * right.variance
-                         ) / this._df;
+    const commonVariance = ((left.size - 1) * left.variance +
+                            (right.size - 1) * right.variance
+                          ) / this._df;
+
+    this._se = Math.sqrt(commonVariance * (1 / left.size + 1 / right.size));
+    this._mean = left.mean - right.mean;
+  }
 
-  this._se = Math.sqrt(commonVariance * (1 / left.size + 1 / right.size));
-  this._mean = left.mean - right.mean;
 }
-util.inherits(StudentT, AbstactStudentT);
+
 module.exports = StudentT;
diff --git a/hypothesis/welch.js b/hypothesis/welch.js
index df4522f..da9f439 100644
--- a/hypothesis/welch.js
+++ b/hypothesis/welch.js
@@ -2,24 +2,26 @@
 
 const Distribution = require('distributions').Studentt;
 
-const util = require('util');
 const AbstactStudentT = require('./abstact.js');
 
-function StudentT(left, right, options) {
-  AbstactStudentT.call(this, options);
+class StudentT extends AbstactStudentT {
+  
+  constructor(left, right, options) {
+    super(options);
 
-  const leftSE = left.variance / left.size;
-  const rightSE = right.variance / right.size;
-  const commonVariance = leftSE + rightSE;
+    const leftSE = left.variance / left.size;
+    const rightSE = right.variance / right.size;
+    const commonVariance = leftSE + rightSE;
 
-  this._df = Math.pow(commonVariance, 2) / (
-    Math.pow(leftSE, 2) / (left.size - 1) +
-    Math.pow(rightSE, 2) / (right.size - 1)
-  );
-  this._dist = new Distribution(this._df);
+    this._df = Math.pow(commonVariance, 2) / (
+      Math.pow(leftSE, 2) / (left.size - 1) +
+      Math.pow(rightSE, 2) / (right.size - 1)
+    );
+    this._dist = new Distribution(this._df);
 
-  this._se = Math.sqrt(commonVariance);
-  this._mean = left.mean - right.mean;
+    this._se = Math.sqrt(commonVariance);
+    this._mean = left.mean - right.mean;
+  }
 }
-util.inherits(StudentT, AbstactStudentT);
+
 module.exports = StudentT;