Ensure that when we check typeof x == 'number' we also check instance…

…of Number (chartjs#5752)

src/core/core.element.js

@@ -42,7 +42,7 @@ function interpolate(start, view, model, ease) {
 						continue;
 					}
 				}
-			} else if (type === 'number' && isFinite(origin) && isFinite(target)) {
+			} else if (helpers.isFinite(origin) && helpers.isFinite(target)) {
 				view[key] = origin + (target - origin) * ease;
 				continue;
 			}

src/core/core.scale.js

@@ -519,7 +519,7 @@ module.exports = Element.extend({
 			return NaN;
 		}
 		// isNaN(object) returns true, so make sure NaN is checking for a number; Discard Infinite values
-		if (typeof rawValue === 'number' && !isFinite(rawValue)) {
+		if ((typeof rawValue === 'number' || rawValue instanceof Number) && !isFinite(rawValue)) {
 			return NaN;
 		}
 		// If it is in fact an object, dive in one more level

src/helpers/helpers.core.js

@@ -51,6 +51,15 @@ var helpers = {
 		return value !== null && Object.prototype.toString.call(value) === '[object Object]';
 	},
 
+	/**
+	 * Returns true if `value` is a finite number, else returns false
+	 * @param {*} value  - The value to test.
+	 * @returns {Boolean}
+	 */
+	isFinite: function(value) {
+		return (typeof value === 'number' || value instanceof Number) && isFinite(value);
+	},
+
 	/**
 	 * Returns `value` if defined, else returns `defaultValue`.
 	 * @param {*} value - The value to return if defined.

src/plugins/plugin.filler.js

@@ -128,7 +128,7 @@ function computeBoundary(source) {
 			return target;
 		}
 
-		if (typeof target === 'number' && isFinite(target)) {
+		if (helpers.isFinite(target)) {
 			horizontal = scale.isHorizontal();
 			return {
 				x: horizontal ? target : null,

test/specs/helpers.core.tests.js

@@ -56,6 +56,24 @@ describe('Chart.helpers.core', function() {
 		});
 	});
 
+	describe('isFinite', function() {
+		it('should return true if value is a finite number', function() {
+			expect(helpers.isFinite(0)).toBeTruthy();
+			// eslint-disable-next-line no-new-wrappers
+			expect(helpers.isFinite(new Number(10))).toBeTruthy();
+		});
+
+		it('should return false if the value is infinite', function() {
+			expect(helpers.isFinite(Number.POSITIVE_INFINITY)).toBeFalsy();
+			expect(helpers.isFinite(Number.NEGATIVE_INFINITY)).toBeFalsy();
+		});
+
+		it('should return false if the value is not a number', function() {
+			expect(helpers.isFinite('a')).toBeFalsy();
+			expect(helpers.isFinite({})).toBeFalsy();
+		});
+	});
+
 	describe('isNullOrUndef', function() {
 		it('should return true if value is null/undefined', function() {
 			expect(helpers.isNullOrUndef(null)).toBeTruthy();