Check if list contains value javascript

Question

I am new to javascript. This is my codes, I want it to return true if it finds 'anna' in the list

var userList = [{'username':'anna','email':'[email protected]'},
               {'username':'benny','email':'[email protected]'},
               {'username':'kathy','email':'[email protected]'}]

return userList.includes('anna')

your help it much appreciated

Josep · Accepted Answer · 2017-04-06 03:19:41Z

6

Use some:

ES6 syntax:

return userList.some(user => user.username === 'anna');

ES5 syntax:

function hasAnna(user) {
  return user.username === 'anna';
}
return userList.some(hasAnna);

edited Apr 6, 2017 at 3:19

answered Apr 6, 2017 at 3:05

Josep

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2 Comments

StackSlave Over a year ago

.some() is cool, just note that IE does not support Arrow functions.

Josep Over a year ago

@PHPglue good point. I've updated the answer. I kind of assume that everyone uses babel these days :-)

Forty3 · Accepted Answer · 2017-04-06 03:02:30Z

2

Try:

return userList.filter(function(e,i) { return e.username == 'anna' }).length > 0;

What this is doing is filtering the array, userList, for all entries with a username value of 'anna' and returning whether or not that filtered list has a length greater than 0 (i.e. has at least one entry).

answered Apr 6, 2017 at 3:02

Forty3

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2 Comments

Josep Over a year ago

While this will work, it's a bit inefficient... Imagine that you have a long list of thousand of items and there is one item that contains 'anna' in the second position. The solution that you are suggesting will iterate through all the items (even if 'anna' was found in the second position). Using some the execution will stop at the second one. I'm giving you a plus one anyways because your answer solves the problem.

Treefish Zhang Over a year ago

Wouldn't a strict comparison using === be more fitting in this case?

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