My tests are not passing because I included a compare method in the Array prototype. What steps can I take to fix this issue in either the

Question

My tests are not passing because I included a compare method in the Array prototype. What steps can I take to fix this issue in either the

Embarking on the challenging Mars Rover Kata has presented a unique problem for me. My jasmine tests are failing because of my array compare method within the prototype. This method is crucial for detecting obstacles at specific grid points.

For instance, my initial test result shows this error: Expected [ 0, 1, 'N', undefined ] to be equal to [ 0, 1, 'N' ].

Upon logging my array, it displays as [0, 1, "N", compare: function]. This discrepancy explains why it doesn't match with [0, 1, 'N'].

The length of my array is 3 and the proto includes the compare method. How can I address this issue?

Access the code branch here. View the tests here.

Update:

I discovered that one of my conditionals was returning undefined, leading to the error of undefined being inserted into my array. Thanks to @GameAlchemist's solution suggestion, I learned about defineProperty and identified the root cause of the problem.

Moreover, based on my research, it is recommended to use Object.defineProperty() or similar methods when adding properties to built-in prototypes to ensure they are non-enumerable. This safeguard helps prevent issues with for-in loops in older code bases.

javascript arrays jasmine

Answer 1

Answer №1

Hiding a prototype property/method in JavaScript can be done using Object.defineProperty and setting it as non-enumerable.

For more information, check out the following link: Object.defineProperty

If you are defining the compare function yourself, use this syntax:

Object.defineProperty(Array.prototype, 'compare', { value : compareFunction } );

By default, configurable, enumerable, and writable are set to false, making the property readonly, non-configurable, and non-enumerable for smooth comparisons.

If you are not the one defining the compare function, ensure that it is still configurable by checking with Object.getOwnPropertyDescriptor or testing with the code provided below:

Object.defineProperty(Array.prototype, 'compare', { value : Array.prototype.compare } );

Similarly, you can iterate over all Array prototypes to verify if each of its properties is enumerable and then make them non-enumerable if needed.

Check out this jsbin link for a demonstration: JSBin Demo

Object.defineProperty(Array.prototype, 'compare', { value : compareArray } );
function compareArray(other) {
  if (!other || other.length != this.length) return false;
  for (var i=0; i<this.length; i++) if (this[i] !== other[i]) return false;
  return true;
}

var a1 = [1, 2, 3, 4];
var a2 = [1, 2, 3, 4];
var a3 = [1, 2, 5, 6];
var a4 = [1, 2];

console.log(' a1 == a2 : ' + a1.compare(a2));
console.log(' a1 == a3 : ' + a1.compare(a3));
console.log(' a1 == a4 : ' + a1.compare(a4));

Answer 2

Hiding a prototype property/method in JavaScript can be done using Object.defineProperty and setting it as non-enumerable.

For more information, check out the following link: Object.defineProperty

If you are defining the compare function yourself, use this syntax:

Object.defineProperty(Array.prototype, 'compare', { value : compareFunction } );

By default, configurable, enumerable, and writable are set to false, making the property readonly, non-configurable, and non-enumerable for smooth comparisons.

If you are not the one defining the compare function, ensure that it is still configurable by checking with Object.getOwnPropertyDescriptor or testing with the code provided below:

Object.defineProperty(Array.prototype, 'compare', { value : Array.prototype.compare } );

Similarly, you can iterate over all Array prototypes to verify if each of its properties is enumerable and then make them non-enumerable if needed.

Check out this jsbin link for a demonstration: JSBin Demo

Object.defineProperty(Array.prototype, 'compare', { value : compareArray } );
function compareArray(other) {
  if (!other || other.length != this.length) return false;
  for (var i=0; i<this.length; i++) if (this[i] !== other[i]) return false;
  return true;
}

var a1 = [1, 2, 3, 4];
var a2 = [1, 2, 3, 4];
var a3 = [1, 2, 5, 6];
var a4 = [1, 2];

console.log(' a1 == a2 : ' + a1.compare(a2));
console.log(' a1 == a3 : ' + a1.compare(a3));
console.log(' a1 == a4 : ' + a1.compare(a4));

Answer 3

Answer №2

maybe this could work:

let newArray = [];
for(let index = 0, length=this.length; index < length; index++) {
    if (this.hasOwnProperty(index)){ 
        // do something here
    }
}

Answer 4

maybe this could work:

let newArray = [];
for(let index = 0, length=this.length; index < length; index++) {
    if (this.hasOwnProperty(index)){ 
        // do something here
    }
}

My tests are not passing because I included a compare method in the Array prototype. What steps can I take to fix this issue in either the

Answer №1

Answer №2

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