How To Use an Array to Pull Values from an Array of Objects

Question

I have an array of reasons a password has failed validation:

const failures = schema.validate(password.value, { list: true });
console.log(failues);
// => [ 'min', 'uppercase', 'digits' ]

I also have an array of objects. The key is always a potential value of the failures array:

const msg = [
  { key: 'min', message: 'minimum' },
  { key: 'max', message: 'maximum' },
  { key: 'uppercase', message: 'need a uppercase' },
  { key: 'lowercase', message: 'need a lowercase' },
  { key: 'digits', message: 'must have digits' },
  { key: 'spaces', message: 'no spaces' },
  { key: 'oneOf', message: 'is not one of' },
];

I want to map over the failures array and return the relevant message from msg to display a more coherent error message.

Michael Bianconi · Accepted Answer · 2019-08-13 15:05:39Z

2

For each value in failures, pull the corresponding item from msg. However, may I suggest creating msg as a dict?

const msg = {
  'min': 'minimum',
  'max': 'maximum',
  ...
};

This will make it easier to do this.

failures.forEach((failure) => {
  if (failure in msg) {
    console.log(msg[failure]);
  }
});

edited Aug 13, 2019 at 15:05

answered Aug 13, 2019 at 14:49

Michael Bianconi

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1 Comment

JABedford Over a year ago

Works a treat. Thank you :)

laruiss · Accepted Answer · 2019-08-13 14:57:09Z

const failures = schema.validate(password.value, { list: true });
console.log(failures);
// => [ 'min', 'uppercase', 'digits' ]

const msg = [
  { key: 'min', message: 'minimum' },
  { key: 'max', message: 'maximum' },
  { key: 'uppercase', message: 'need a uppercase' },
  { key: 'lowercase', message: 'need a lowercase' },
  { key: 'digits', message: 'must have digits' },
  { key: 'spaces', message: 'no spaces' },
  { key: 'oneOf', message: 'is not one of' },
];

const listOfMessages = msgs
  .filter(msg => failures.includes(msg.key)) // Get the appropriate object matching the error
  .map(msg => msg.message) // Only get the message

console.log(listOfMessages) // ['minimum', 'need a uppercase', 'must have digits']

r3wt · Accepted Answer · 2019-08-13 14:56:00Z

1

You can use array.filter() and array.map() to achieve what you want:

const messages = msg.filter(r=>failures.indexOf(r.key)!==-1).map(r=>r.message)// ["minimum", "need a uppercase", "must have digits"]

What you do with it from here is up to you, as even if you join the messages array, it doesn't form a coherent sentence. I also agree with the recommendation above to switch to a Dict like Object instead of the array of objects you are using now.

answered Aug 13, 2019 at 14:56

r3wt

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Comments

Thomas · Accepted Answer · 2019-08-13 15:06:25Z

// this is a very verbose way to store this information, also hard to fetch by key
const msg = [
  { key: 'min', message: 'minimum' },
  { key: 'max', message: 'maximum' },
  { key: 'uppercase', message: 'need a uppercase' },
  { key: 'lowercase', message: 'need a lowercase' },
  { key: 'digits', message: 'must have digits' },
  { key: 'spaces', message: 'no spaces' },
  { key: 'oneOf', message: 'is not one of' },
];

const failures = [
  'min',
  'uppercase',
  'digits',
  'something-not-mapped'
];


// better use a map
const msg2 = msg.reduce((acc, item) => {
  acc[item.key] = item.message;
  return acc;
}, {});
console.log("msg2:", msg2);

// now you can do:
console.log("mapped failures:", failures.map(key => msg2[key] || key));

.as-console-wrapper{top:0;max-height:100%!important}

I think with the comments, this code is self-explanatory.

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