this.state.count.

this.state = {
        selection: {start: 0, end: 0},
        noCents: true,
        firstFocus: true,
        count: 0
    };
    
setSelection = () => {
    if (this.state.firstFocus) {
        this.setState({selection: {start: 1, end: 1}});
        this.setState({firstFocus: false})
    }
};
    
doJob(amount) {
    if (this.state.count === 2 && !this.state.noCents) {
        this.setState({
            count: 0,
            noCent: true
        })
    }
    if (amount.length !== 0 && this.state.noCents) {
        this.setState({
            selection: {
                start: amount.length - 3,
                end: amount.length - 3
            }
        });
    } else if (amount.length !== 0 && !this.state.noCents) {
        this.setState({count: this.state.count + 1});
        if (this.state.count === 1) {
            this.setState({
                selection: {
                    start: amount.length - 2,
                    end: amount.length - 2
                },
            });
        }
        if (this.state.count === 2) {
            this.setState({
                selection: {
                    start: amount.length - 1,
                    end: amount.length - 1
                },
            });
        }}
}
    
<TextInputMask
       style={styles.input}
       type={'money'}
       options={{
          precision: 2,
          separator: ',',
          delimiter: '.',
          unit: '',
          suffixUnit: '',
          zeroCents: this.state.noCents
          }}
      value={this.props.amount}
      onChangeText={amount => this.props.amountChanged({
             props: 'amount',
             value: amount
           },
             this.doJob(amount))}
  onFocus={this.setSelection}
  selection={this.state.selection}
  onKeyPress={(e) => (e.nativeEvent.key === ',' ? this.setState({noCents: false}) : null)}
/>