setting-state.js

addLike() {
    //this.state.transactionList = fdjskflds // DO NOT CHANGE STATE DIRECTLY
    // let something = this.state.transactionList.push({ fdjskfldsfjklds }) // DO NOT CHANGE STATE DIRECTLY
    // this.setState({ transactionList: something })

    this.setState(state => ({ numLikes: state.numLikes + 1 }) )

    // adding
    this.setState( state => ({ transactionList: [ ...state.transactionList, "fdsfdsfsd"] }) )
    this.setState( state => ({ transactionList: state.transactionList.concat(["fdsfdsfsd"]) }) )

    // deleting
    this.setState( state => ({ transactionList: state.transactionList.filter(t => t.id !== idToDelete ) }) )

    // update one transaction
    this.setState( state => ({ transactionList: state.transactionList.map(t => {
                if(t.id === idToUpdate) {
                    return { ...t, amount: 20 }
                }
                else {
                    return t;
                }
            })
        })
    )

    // simplified version of previous
    this.setState( state => ({ transactionList: state.transactionList.map( t => (t.id === idToUpdate) ? { ...t, amount: 20 } : t ) }) )

    // stretched out version of previous
    this.setState( state => {
        const newTransactionList = [...state.transactionList]
        newTransactionList[3] = { ...newTransactionList[3], amount: 20 }
        return { transactionList: newTransactionList }
    })

    //this.state.transactionList[3] = { ...transactionToUpdate, amount: 20 } // DO NOT CHANGE STATE DIRECTLY
}


// TODO
// { people: [ Simone, Maria, Chance ]}
// { people: [ Simone ]}