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#
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Input: func = () => expect( 5 ). toBe ( 5 )
Output: { "value" : true }
Explanation: 5 === 5 so this expression returns true .
Example 2#
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Input: func = () => expect( 5 ). toBe ( null )
Output: { "error" : "Not Equal" }
Explanation: 5 !== null so this expression throw the error "Not Equal" .
Example 3#
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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
Javascript
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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)`