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JavaScript JavaScript Unit Testing Behavior Driven Development with Mocha & Chai Writing Our First Test Suite - Part 2

Jay Azares
Jay Azares
16,600 Points
Posted by Jay Azares
Jay Azares
16,600 Points

Getting this error in Mocha testing: TypeError: Cannot read property 'filter' of undefined

Here's my code....am I missing something?

JAVASCRIPT:

function checkForShip (player, coordinates) { var shipPresent, ship;

for (var i = 0; i < player.ships.length; i++) {
    ship = player.ships[i];

    shipPresent = ship.locations.filter(function (actualCoordinate) {
        return (actualCoordinate[0] === coordinates[0]) && (actualCoordinate[1] === coordinates[1]);
    })[0];

    if (!shipPresent) {
        return false;
    } else {
        return true;
    }
}

}

module.exports.checkForShip = checkForShip;

MOCHA:

Mocha √ should run our tests using npm

checkForShip 1) should correctly report no ship at a given players coordinate 2) should correctly report a ship located at the given coordinates 3) should handle ships at more than one coordinate

1 passing (18ms) 3 failing

1) checkForShip should correctly report no ship at a given players coordinate: TypeError: Cannot read property 'filter' of undefined at checkForShip (game_logic\ship_methods.js:7:37) at Context.<anonymous> (test\ship_test.js:16:16)

2) checkForShip should correctly report a ship located at the given coordinates: TypeError: Cannot read property 'filter' of undefined at checkForShip (game_logic\ship_methods.js:7:37) at Context.<anonymous> (test\ship_test.js:29:16)

3) checkForShip should handle ships at more than one coordinate: TypeError: Cannot read property 'filter' of undefined at checkForShip (game_logic\ship_methods.js:7:37) at Context.<anonymous> (test\ship_test.js:41:16)

2 Answers

Up&Up Agency
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Up&Up Agency
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Up&Up Agency
Up&Up Agency
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It is likely due to the structure of your player object. The JS interpreter cannot run the filter() function on something that is not an array.

Check the player object you are passing into the function and make sure that player.ships is an array of location objects that contain an array of locations.

jennyhan
jennyhan
36,121 Points
jennyhan
jennyhan
36,121 Points

It should because that you didn't define the ship object correctly. Did you create a player object exactly like this: 

player = {
      ships: [
        {
          locations: [[0, 0]]
        }
      ]
    };