Add ability to properly cast a string, number, null to an integer (#990)

front/src/utils/__tests__/cast-as-integer-or-null.test.ts

@@ -0,0 +1,72 @@
+import {
+  canBeCastAsIntegerOrNull,
+  castAsIntegerOrNull,
+} from '../cast-as-integer-or-null';
+
+describe('canBeCastAsIntegerOrNull', () => {
+  it(`should return true if null`, () => {
+    expect(canBeCastAsIntegerOrNull(null)).toBeTruthy();
+  });
+
+  it(`should return true if number`, () => {
+    expect(canBeCastAsIntegerOrNull(9)).toBeTruthy();
+  });
+
+  it(`should return true if empty string`, () => {
+    expect(canBeCastAsIntegerOrNull('')).toBeTruthy();
+  });
+
+  it(`should return true if integer string`, () => {
+    expect(canBeCastAsIntegerOrNull('9')).toBeTruthy();
+  });
+
+  it(`should return false if undefined`, () => {
+    expect(canBeCastAsIntegerOrNull(undefined)).toBeFalsy();
+  });
+
+  it(`should return false if non numeric string`, () => {
+    expect(canBeCastAsIntegerOrNull('9a')).toBeFalsy();
+  });
+
+  it(`should return false if non numeric string #2`, () => {
+    expect(canBeCastAsIntegerOrNull('a9a')).toBeFalsy();
+  });
+
+  it(`should return false if float`, () => {
+    expect(canBeCastAsIntegerOrNull(0.9)).toBeFalsy();
+  });
+
+  it(`should return false if float string`, () => {
+    expect(canBeCastAsIntegerOrNull('0.9')).toBeFalsy();
+  });
+});
+
+describe('castAsIntegerOrNull', () => {
+  it(`should cast null to null`, () => {
+    expect(castAsIntegerOrNull(null)).toBe(null);
+  });
+
+  it(`should cast empty string to null`, () => {
+    expect(castAsIntegerOrNull('')).toBe(null);
+  });
+
+  it(`should cast an integer to an integer`, () => {
+    expect(castAsIntegerOrNull(9)).toBe(9);
+  });
+
+  it(`should cast an integer string to an integer`, () => {
+    expect(castAsIntegerOrNull('9')).toBe(9);
+  });
+
+  it(`should throw if trying to cast a float string to an integer`, () => {
+    expect(() => castAsIntegerOrNull('9.9')).toThrow(Error);
+  });
+
+  it(`should throw if trying to cast a non numeric string to an integer`, () => {
+    expect(() => castAsIntegerOrNull('9.9a')).toThrow(Error);
+  });
+
+  it(`should throw if trying to cast an undefined to an integer`, () => {
+    expect(() => castAsIntegerOrNull(undefined)).toThrow(Error);
+  });
+});

front/src/utils/cast-as-integer-or-null.ts

@@ -0,0 +1,58 @@
+export function canBeCastAsIntegerOrNull(
+  probableNumberOrNull: string | undefined | number | null,
+): probableNumberOrNull is number | null {
+  if (probableNumberOrNull === undefined) {
+    return false;
+  }
+
+  if (typeof probableNumberOrNull === 'number') {
+    return Number.isInteger(probableNumberOrNull);
+  }
+
+  if (probableNumberOrNull === null) {
+    return true;
+  }
+
+  if (probableNumberOrNull === '') {
+    return true;
+  }
+
+  if (typeof probableNumberOrNull === 'string') {
+    const stringAsNumber = +probableNumberOrNull;
+
+    if (isNaN(stringAsNumber)) {
+      return false;
+    }
+    if (Number.isInteger(stringAsNumber)) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+export function castAsIntegerOrNull(
+  probableNumberOrNull: string | undefined | number | null,
+): number | null {
+  if (canBeCastAsIntegerOrNull(probableNumberOrNull) === false) {
+    throw new Error('Cannot cast to number or null');
+  }
+
+  if (probableNumberOrNull === null) {
+    return null;
+  }
+
+  if (probableNumberOrNull === '') {
+    return null;
+  }
+
+  if (typeof probableNumberOrNull === 'number') {
+    return probableNumberOrNull;
+  }
+
+  if (typeof probableNumberOrNull === 'string') {
+    return +probableNumberOrNull;
+  }
+
+  return null;
+}