How to hold index of object inside of array?

Question

I'm trying to code "blockchain" visual implementation in React. I want to hold somehow inside array of objects(that are my blocks) index of each object. I can't figure out how to do it.

    this.state = {
      value: '',
      blocks: [{
        hash: calculateHash(1),
        timestamp: timeStamp(),
        dataOfBlock: 'Genesis Block',
        nounce: 607,
        index: 0
      }]
    }
  };

    addBlock = (event) => {
      event.preventDefault();

      this.setState({
      blocks: [...this.state.blocks, {
        hash: 'cos',
        timestamp: timeStamp(),      
        dataOfBlock: this.state.value,
        nounce: '',
        index: 1 // here's the problem
      }]
    })
    }

My code mimics what i want to accomplish where the comment is. I want to constantly add +1 to my index with each block.

if your always adding to the end of the array, you can make index this.state.blocks.length because the length of the prev array will be the index point of the new block — pengcheng95
– pengcheng95, Commented Feb 5, 2019 at 17:59
index: this.state.blocks.length+1, suggestion: use prevState instead of this.state inside setState. — Mayank Shukla
– Mayank Shukla, Commented Feb 5, 2019 at 17:59

Maheer Ali · Accepted Answer · 2019-02-05 18:00:18Z

4

You can use length as index of new object when adding new object
Note: this.state.blocks.length will the next index because index start from 0

blocks: [...this.state.blocks, {
        hash: 'cos',
        timestamp: timeStamp(),      
        dataOfBlock: this.state.value,
        nounce: '',
        index: this.state.blocks.length
      }]

answered Feb 5, 2019 at 18:00

Maheer Ali

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