feat: Add isNegativeNumber, isPositiveNumber, and isNonZeroNumber (#67)

Author: wweaver

src/index.spec.ts

@@ -53,6 +53,24 @@ describe('ts-util-is methods', () => {
     expect(util.isNumber(83)).toEqual(true);
   });
 
+  it('ensure value is a non-zero number', () => {
+    expect(util.isNonZeroNumber(-1)).toEqual(true);
+    expect(util.isNonZeroNumber(0)).toEqual(false);
+    expect(util.isNonZeroNumber(1)).toEqual(true);
+  });
+
+  it('ensure value is a positive number', () => {
+    expect(util.isPositiveNumber(-1)).toEqual(false);
+    expect(util.isPositiveNumber(0)).toEqual(false);
+    expect(util.isPositiveNumber(1)).toEqual(true);
+  });
+
+  it('ensure value is a negative number', () => {
+    expect(util.isNegativeNumber(1)).toEqual(false);
+    expect(util.isNegativeNumber(0)).toEqual(false);
+    expect(util.isNegativeNumber(-1)).toEqual(true);
+  });
+
   it('ensure value is an object', () => {
     expect(util.isObject({})).toEqual(true);
   });

src/index.ts

@@ -116,6 +116,33 @@ export function isNumber(value: any): value is number {
   return typeof value === 'number';
 }
 
+/**
+ * Determines if a reference is a non-zero `Number`.
+ *
+ * @param value Reference to check.
+ */
+export function isNonZeroNumber(value: unknown): value is number {
+  return typeof value === 'number' && !!value;
+}
+
+/**
+ * Determines if a reference is a positive `Number`.
+ *
+ * @param value Reference to check.
+ */
+export function isPositiveNumber(value: unknown): value is number {
+  return typeof value === 'number' && value > 0;
+}
+
+/**
+ * Determines if a reference is a negative `Number`.
+ *
+ * @param value Reference to check.
+ */
+export function isNegativeNumber(value: unknown): value is number {
+  return typeof value === 'number' && value < 0;
+}
+
 /**
  * Determines if a reference is an 'Object'.
  *