How to generate permanent React keys for same string value in array?

Question

I have a textbox where a user enters text. A search for specific keywords is then performed and the string is split at these keywords.

A first input may look like E.g.

[
    0: "this is "
    1: "word"
    2: " a form field value with another "
    3: "word"
]

A change then might be made to remove the first repeated word:

[
    0: "this is "
    1: " a form field value with another "
    2: "word"
]

How can I create a persistent key for each array item? I need the second word value to have the same React key as when it is first generated regardless of array position. It is a separate component instance regardless of the same value. I have an issue right now where deleting one of the split words will delete both due to the keys changing after the first word is deleted.

Best practices say not to use the array index, but I'm unsure in this situation how else to generate a unique key.

In your case it seems like you can probably use Index only or combine index with word content like ${index}${value} — Rikin
– Rikin, Commented Mar 30, 2020 at 16:38
Thanks @xdeepakv, but keys need to be unique. Same words would have same key. — Rob Fyffe
– Rob Fyffe, Commented Mar 30, 2020 at 17:04

xdeepakv · Accepted Answer · 2020-03-30 16:53:38Z

2

This is a rough solution, but you can think of as a dictionary program.

class SomeComponent {
  constructor() {
    this.state = {
      words: ["this is ", "word", " a form field value with another ", "word"]
    };
    this.wordMap = this.state.words.reduce((m, x, index) => {
      m[index] = x;
      return m;
    }, {});
  }
  cleanWord() {
    let unique = new Set();
    for (let key in this.wordMap) {
      if (unique.has(this.wordMap[key])) {
        this.wordMap[key] = null; //duplicate
      } else {
        unique.add(this.wordMap[key]);
      }
    }
  }
  onDelete(index) {
    this.wordMap[index] = null;
  }
}
const dict = new SomeComponent();
dict.cleanWord();
console.log(dict.wordMap);

dict.onDelete(1);
console.log(dict.wordMap);

.as-console-row {color: blue!important}

answered Mar 30, 2020 at 16:53

xdeepakv

8,1452 gold badges25 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Rob Fyffe Over a year ago

I ended up going with a solution like this.

Code Maniac · Accepted Answer · 2020-03-30 16:42:25Z

0

You can use value as key, and keep the indexes as values

[
    "this is ": [0]
    "word": [1,3]
    " a form field value with another ":[2]
]

And then when you remove one index it will look like

[
    "this is ": [0]
    "word": [3]
    " a form field value with another ":[2]
]

You can use reduce to produce such format from your splitted string

let str = ["this is ", "word", " a form field value with another ", "word"]

let mapperObj = str.reduce((op, inp, index) => {
  op[inp] = op[inp] || []
  op[inp].push(index)
  return op
}, {})

console.log(mapperObj)

answered Mar 30, 2020 at 16:42

Code Maniac

37.9k5 gold badges44 silver badges65 bronze badges

1 Comment

Code Maniac Over a year ago

@RobFyffe these are, you can never have duplicate property name in object

Ryan Ward · Accepted Answer · 2020-03-30 16:46:18Z

0

You can use anything as the key, to the best of my knowledge, but you want them to be unique for each item.

I'd recommend base64'ing your item using btoa(JSON.stringify(object)) or creating a unique key like mentioned above by appending index to value, ${index}${value}

answered Mar 30, 2020 at 16:46

Ryan Ward

111 bronze badge

1 Comment

Rob Fyffe Over a year ago

In React the keys must be unique. The same words would have the same key. Then removing the a value from the array would change the index so this means the key would not be persistent.

xadm · Accepted Answer · 2020-03-30 17:18:27Z

0

You can use index as key if you can mark deleted values as null. This value can be rendered without additional filtering.

answered Mar 30, 2020 at 17:18

xadm

8,4463 gold badges17 silver badges27 bronze badges

Collectives™ on Stack Overflow

How to generate permanent React keys for same string value in array?

4 Answers 4

1 Comment

1 Comment

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

1 Comment

1 Comment

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related