state = {
    editDueDateText: ''
}

onChangeEditDueDate = (event) => {
    this.setState({
      editDueDateText: event.target.value
    })
  }

editDueDate = (e, keyName, dueDateObject) => {
    dueDateObject.showEditDate = false;
    this.props.editDueDate({ keyName, dueDateObject, editText: this.state.editDueDateText })
  }

<input className="form-control"
              onKeyDown={(e) => this.editDueDatekeypress(e, keyName, dueDateObject)}
              onChange={this.onChangeEditDueDate}
              value={this.state.editDueDateText}
              defaultValue={dueDateObject.dueDate}
              type="text"
              placeholder="By 28th May, I will have" />
            <div className="input-group-append">
              <button className="btn btn-outline-primary"
                type="button"
                onClick={(e) => this.editDueDate(e, keyName, dueDateObject)}>Submit</button>
            </div>