javascript - How to find the key of the min value in a hash with underscore - Stack Overflow

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I would like to find the key of a minimum value with underscore. For example:

var my_hash = {'0-0' : {value: 23, info: 'some info'},
              '0-23' : {value: 8, info: 'some other info'},
              '0-54' : {value: 54, info: 'some other info'},
              '0-44' : {value: 34, info: 'some other info'}
              }
find_min_key(my_hash); => '0-23'

How can I do that with underscorejs ?

I've tried:

_.min(my_hash, function(r){
  return r.value;
});
# I have an object with the row, but not it's key
# => Object {value: 8, info: "some other info"}

I also try to sort it (and then getting the first element):

_.sortBy(my_hash, function(r){ 
  return r.value; 
})

But it returns an array with numerical indexes, so my hash keys are lost.

I would like to find the key of a minimum value with underscore. For example:

var my_hash = {'0-0' : {value: 23, info: 'some info'},
              '0-23' : {value: 8, info: 'some other info'},
              '0-54' : {value: 54, info: 'some other info'},
              '0-44' : {value: 34, info: 'some other info'}
              }
find_min_key(my_hash); => '0-23'

How can I do that with underscorejs ?

I've tried:

_.min(my_hash, function(r){
  return r.value;
});
# I have an object with the row, but not it's key
# => Object {value: 8, info: "some other info"}

I also try to sort it (and then getting the first element):

_.sortBy(my_hash, function(r){ 
  return r.value; 
})

But it returns an array with numerical indexes, so my hash keys are lost.

• javascript
• underscore.js

Share Improve this question Follow edited Feb 26, 2014 at 18:29 Benjamin Crouzier asked Feb 26, 2014 at 18:23 Benjamin CrouzierBenjamin Crouzier 42k4848 gold badges177177 silver badges239239 bronze badges

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3 Answers 3

Sorted by: Reset to default 8

With Underscore or Lodash < 4:

_.min(_.keys(my_hash), function(k) { return my_hash[k].value; }); //=> 0-23

With Lodash >= 4:

_.minBy(_.keys(my_hash), function(k) { return my_hash[k].value; }); //=> 0-23

Without a library:

Object.entries(my_hash).sort((a, b) => a[1].value - b[1].value)[0][0]

or

Object.keys(my_hash).sort((a, b) => my_hash[a].value - my_hash[b].value)[0]

You can do this with reduce:

var result = _.reduce(my_hash, function(memo, val, key) {
  if (val.value < memo.value || _.isNull(memo.value)) {
    return {key: key, value: val.value};
  } else {
    return memo;
  }
}, {key: "none", value: null});
console.log(result.key);

Outputs:

0-23

_.reduce(my_hash, function(m, v, k, l) {
  if (v.value <= l[m].value) {
    m = k;
  }
  return m;
}, '0-0');

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