To Be Or Not To Be

Problem

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".

Examples

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.

## Solution

### Method 1 – JavaScript Closure

#### Intuition

Use a closure to capture the value and return an object with the required methods.

#### Approach

Return an object with `toBe` and `notToBe` methods, each throwing or returning as specified.

#### Code

{{< code_tabs >}}
##### JavaScript
```javascript
function expect(val) {
    return {
        toBe: function(other) {
            if (val === other) return true;
            throw new Error("Not Equal");
        },
        notToBe: function(other) {
            if (val !== other) return true;
            throw new Error("Equal");
        }
    };
}

Complexity

• ⏰ Time complexity: O(1)
• 🧺 Space complexity: O(1)