I have an array of objects in javascript like this:

array=[{label: 1, value:e}, {label:1, value: i}, {label: 2, value:l}]

I want to find the label when value is l so I'm writing:

array.map((i) => i.find(item => item.value === 'l').label)

But an error is returning

i.find is not a function

What am I missing?

I have an array of objects in javascript like this:

array=[{label: 1, value:e}, {label:1, value: i}, {label: 2, value:l}]

I want to find the label when value is l so I'm writing:

array.map((i) => i.find(item => item.value === 'l').label)

But an error is returning

i.find is not a function

What am I missing?

• javascript
• find

• Is the second code line plete? Seems to me you are missing a ( somewhere. – Manfred Radlwimmer Commented Jun 7, 2017 at 10:49
• 1 Yes an ( is missing. My mistake but the error is still here – RamAlx Commented Jun 7, 2017 at 10:50

3 Answers 3

I don't understand why you are using map- based on your question you are just trying to find the label of the element with a particular value, so all you need is find. This works fine:

array.find(item => item.value === 'l').label

Returns 2.

You should handle the case where find returns undefined, for example:

var found = array.find(item => item.value === 'l')
if(found){
  var label = found.label;
  // use label
}else{
  // nothing found
}

In your case, i bees {label: 1, value:e}, then moves on to your next objects from the array. Those objects don't have a .find method. Instead, you can simply use the i.value to extract the information.

If you only want to produce an output for some of the elements, you need to filter them first, then map:

let labels = array
  .filter(i => i.value === 'l')
  .map(i => i.label)
;

You are using the map function before your find, please see the documentation on the two function

• https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
• https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

I believe to achieve the oute you desire you just want to use the find on it's own.

In your example code the i variable is the object within your array not an array.