30 Days of Javascript 3 - To Be Or Not To Be

Write a function expect that helps developers test their code. It should take in any value val and return an object with the following two functions.

toBe(val) accepts another value and returns true if the two values === each other. If they are not equal, it should throw an error “Not Equal”. notToBe(val) accepts another value and returns true if the two values !== each other. If they are equal, it should throw an error “Equal”.

Example 1:

Input: func = () => expect(5).toBe(5) Output: {“value”: true} Explanation: 5 === 5 so this expression returns true. Example 2:

Input: func = () => expect(5).toBe(null) Output: {“error”: “Not Equal”} Explanation: 5 !== null so this expression throw the error “Not Equal”. Example 3:

Input: func = () => expect(5).notToBe(null) Output: {“value”: true} Explanation: 5 !== null so this expression returns true.

/**
 * @param {string} val
 * @return {Object}
 */
var expect = function (val) {
  return {
    toBe: function (toVal) {
      if (val === toVal) {
        return true;
      } else {
        throw new Error("Not Equal");
      }
    },
    notToBe: function (notToVal) {
      if (val !== notToVal) {
        return true;
      } else {
        throw new Error("Equal");
      }
    },
  };
};
/**
 * expect(5).toBe(5); // true
 * expect(5).notToBe(5); // throws "Equal"
 */

This expect function takes in a value val and returns an object with two functions: toBe and notToBe.

The toBe function compares the value val with another value toVal using the strict equality operator (===). If the two values are equal, it returns true. Otherwise, it throws an error with the message "Not Equal".

The notToBe function compares the value val with another value notToVal using the strict inequality operator (!==). If the two values are not equal, it returns an object with the value property set to true. Otherwise, it throws an error with the message "Equal".