I am newbie with javascript and meet a problem like this.

For example . there is a variable with a list like this

{
    name: 'x',
    attack: 50,
    speed: 100,
    hitpoint: 100,
},
{
    name: 'y',
    attack: 150,
    speed: 80,
    hitpoint: 180,
}

Find an variable with an attack = 150 and return it in the function "findAMonsterByAttack" If there is no matching variable in the list of variable, the "findAMonsterByAttack" function returns null.

Here is my code :

function findAMonsterByAttack(monsters) {
var monsters = [
{
    name: 'x',
    attack: 50,
    speed: 100,
    hitpoint: 100,
},
{
    name: 'y',
    attack: 150,
    speed: 80,
    hitpoint: 180,
},
// ...
];
var isfree = monsters.every(function(course, index) {
return course.attack ===150;
});

My idea is using the code every to check course and index, then return if the attach = 150. But I failed. Could you please help me with this case ? Thank you very much for your time.

CodePudding user response：

If monsters is an array, you can use array.filter to return another array with of only the monsters with matching criteria

eg attack === 150.

Note that there could be multiple matches, so this would return an array with all of the monsters that match, (or an empty array if no monsters match).

const monsters = [{
    name: 'x',
    attack: 50,
    speed: 100,
    hitpoint: 100,
  },
  {
    name: 'y',
    attack: 150,
    speed: 80,
    hitpoint: 180,
  },
  {
    name: 'z',
    attack: 150,
    speed: 90,
    hitpoint: 150,
  }
]

const a150 = monsters.filter(m => m.attack === 150)

console.log(a150)

<iframe name="sif1" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

If you only care about one monster, you could also use array.find. But this would return the first monster found and undefined if no matches are found.

const monsters = [{
    name: 'x',
    attack: 50,
    speed: 100,
    hitpoint: 100,
  },
  {
    name: 'y',
    attack: 150,
    speed: 80,
    hitpoint: 180,
  },
  {
    name: 'z',
    attack: 150,
    speed: 90,
    hitpoint: 150,
  }
]

const a150 = monsters.find(m => m.attack === 150)

console.log(a150)

<iframe name="sif2" sandbox="allow-forms allow-modals allow-scripts" frameborder="0"></iframe>

Note: array.every tests whether all monsters meet the criteria and returns a Boolean value. In your example this will return false because all monsters do not have an attack value of 150.

CodePudding user response：

Is this what you want?

function findAMonsterByAttack() {
var monsters = [
{
    name: 'x',
    attack: 50,
    speed: 100,
    hitpoint: 100,
},
{
    name: 'y',
    attack: 150,
    speed: 80,
    hitpoint: 180,
}
// ...
];

for ( m of monsters ) {
  if ( m.attack == 150 )
    return m
}
return "Monster with attack 150 not found"
}

console.log(findAMonsterByAttack())